Electrolysis device

ABSTRACT

An electrolysis device of the present invention includes an electrolysis unit. The electrolysis unit includes a channel for fluid to be treated, at least one electrolysis electrode pair, a flow inlet, and a flow outlet. The electrolysis electrode pair is disposed so as to incline with respect to a vertical direction and includes an upper electrode and a lower electrode disposed so as to face each other. The channel for fluid to be treated is disposed so that a fluid that has flowed in from the flow inlet flows through an interelectrode channel between the upper electrode and the lower electrode from a lower side to an upper side and flows out from the flow outlet.

TECHNICAL FIELD

The present invention relates to an electrolysis device and particularly to a diaphragmless electrolysis device.

BACKGROUND ART

Electrolysis is practically used for, for example, production of chemical materials. Basic chemical raw materials such as sodium hydroxide (caustic soda), chlorine gas, hydrogen gas, and sodium carbonate (soda ash) are produced by, for example, an electrolytic soda process. In addition to industrial uses, an electrolysis technique is also used for home appliances such as an alkaline ionized water filter.

The advantage of such an electrolysis technique is that an active substance can be produced from a harmless material having almost no activity. For example, hypochlorites such as sodium hypochlorite is used as a bleaching agent and a germicide for treating clean and sewage water, for treating a drain, and for household kitchens and washing. Hypochlorites are produced by a method in which an alkali hydroxide obtained by electrolysis of an aqueous solution of an alkali metal chloride, such as a saline solution, is caused to react with chlorine gas or a method in which an aqueous solution of an alkali metal chloride is electrolyzed in a diaphragmless electrolytic cell and an aqueous hypochlorite solution is produced in the electrolytic cell.

By the method in which an alkali hydroxide is caused to react with chlorine gas, a high-concentration aqueous hypochlorite solution can be obtained. Therefore, when an aqueous hypochlorite solution is produced for sale, this method is employed. However, since electrolysis facilities for producing an alkali hydroxide and chlorine gas are required, this method is performed at a large-scale electrolysis plant for alkali chlorides such as a common salt together with the production of an alkali hydroxide or chlorine gas.

By the method in which an aqueous solution such as a saline solution is electrolyzed in a diaphragmless electrolytic cell, an aqueous hypochlorite solution having a concentration allowable for direct use for clarification and sterilization of water can be produced using simple electrolysis facilities. Therefore, this method is employed at a site where an aqueous hypochlorite solution is actually used. Furthermore, in the production of the aqueous hypochlorite solution by electrolysis, the electric current applied can be adjusted in accordance with the amount of an aqueous hypochlorite solution required, and all the chlorine component effective for sterilization or the like is dissolved in water. Therefore, the method for producing an aqueous hypochlorous acid solution by electrolysis has an advantage of not requiring storage and transport of hypochlorites. Thus, the production of an aqueous hypochlorite solution by electrolysis is performed even at a plant where a facility for storing liquid chlorine is installed to use chlorine gas or a plant where a high-concentration aqueous hypochlorite solution is stored to use an aqueous hypochlorite solution.

In the method for producing a hypochlorite by electrolysis of an aqueous solution of an alkali metal chloride, an anodic reaction represented by reaction formulae (1) to (3) and a cathodic reaction represented by reaction formula (4) are believed to proceed.

2Cl⁻→Cl₂+2e ⁻  (1)

Cl₂+H₂O→HCl+HClO  (2)

H₂O→1/2O₂+2H⁺+2e ⁻  (3)

2H₂O+2e ⁻→H₂+2OH⁻  (4)

When the aqueous solution becomes strongly acidic (pH: 3 or less), the rate of the reaction represented by the reaction formula (2) decreases, which may result in production of chlorine gas due to a reverse reaction.

However, when the concentration of an aqueous hypochlorite solution produced by electrolysis is low, the concentration of an organic material contained in water to be treated is sometimes increased, or an object to be disinfected to which a relatively large amount of an organic material adheres cannot be sometimes sufficiently disinfected. A high-concentration aqueous hypochlorite solution is believed to be produced by a method in which an electrolysis solution is held between the anode and the cathode for a long time or a method that uses a multistage electrolysis unit including a plurality of electrolytic cells each including an anode and a cathode and disposed with partitions therebetween. However, a long hold time decreases the production amount per unit time, and use of multistage electrodes degrades the productivity and increases the cost. Furthermore, when these methods are employed, a large amount of hydrogen gas is generated. Consequently, the contact area between the electrolysis solution and the electrode decreases as a result of adhesion of air bubbles. Furthermore, the production efficiency of an electrolysis product decreases and the concentration of the aqueous hypochlorite solution varies because of shielding of an electric field or the like.

Since an acidic aqueous solution with a low hydrogen ion exponent (pH) has disinfectant properties, the production of an aqueous hypochlorite solution having a relatively low hypochlorite concentration and a low pH may be adopted. Thus, an aqueous hypochlorite solution having sufficient disinfectant properties can be produced while the required power consumption is reduced. However, use of such an acidic aqueous hypochlorite solution tends to generate chlorine gas in addition to hydrogen gas.

A known production apparatus of an aqueous hypochlorite solution by electrolysis will be described with reference to FIGS. 15 to 17.

FIG. 15 schematically illustrates a known electrolysis device 100 generally used for products obtained with an electrolysis technique. An electrode pair including a first electrode 103 and a second electrode 104 is disposed inside a resin casing 101. A wiring line 106 (pin) for applying a voltage is connected to the first electrode 103, and a wiring line 107 (pin) for applying a voltage is connected to the second electrode 104. Typically, one end of the pin is welded to the electrode and the other end of the pin is threaded so as to be connected to a wiring line from a power supply. Although the shape of the casing 101 can be suitably contrived using an O-ring or the like to prevent liquid leakage, this contrivance is omitted because it is not directly related to the present invention. The electrolysis device 100 includes a supply inlet 108 from which a liquid to be treated is supplied between the electrodes and a discharge outlet 109 from which a liquid subjected to electrolysis is discharged. Normally, the electrode pair is disposed in the vertical direction, and the liquid to be treated is supplied from the lower side.

In such a configuration, when gas is generated by an electrolysis reaction and air bubbles are present on the electrode surface, the air bubbles can be easily removed from the electrode surface by buoyancy of the air bubbles and flow of the liquid to be treated. Consequently, a decrease in the area of the electrode surface on which an electrolysis reaction proceeds can be suppressed. In such a configuration, however, the flow velocity of an electrolysis solution around the center of an interelectrode channel is high, and the flow velocity of an electrolysis solution around the ends is low. Therefore, the time for which the electrolysis solution is electrolyzed varies depending on the paths through which the electrolysis solution flows, which decreases the production efficiency of an electrolysis product.

An example of products for which the electrolysis device is used is an electrolyzed water-producing device 120 in FIG. 16. The electrolysis device is desirably made compact in size as much as possible and installed to the electrolyzed water-producing device 120. A casing 111 includes a feed water inlet 112 that can be connected to a pipe through which water is supplied from a water supply or another water source under pressure and a discharge outlet 113 from which the electrolyzed water is discharged. A pipe through which the electrolyzed water is fed to a supply target can be connected to the discharge outlet 113. An ON/OFF switch 114 for the device is also disposed. In addition, an indicator that displays an operation status and other switches used for various operations may be suitably disposed, but they are omitted because they are not directly related to the present invention.

FIG. 17 schematically illustrates an internal structure of the electrolyzed water-producing device 120 in FIG. 16. The feed water inlet 112 and the discharge outlet 113 are connected to each other through a pipe 115, and a solenoid-controlled valve 116 used for ON/OFF control may be optionally disposed therebetween. The pipe 115 includes a portion spatially connected to an outlet of the electrolysis device 100. An inlet of the electrolysis device 100 is spatially connected to a raw solution tank 117 through a pipe such as a tube. A pump 118 for feeding a raw solution by a predetermined amount is disposed between the electrolysis device 100 and the raw solution tank 117.

Next, a fundamental operation of the electrolyzed water-producing device 120 will be described. When the switch 114 is turned ON, the solenoid-controlled valve 116 is opened and water is supplied from the feed water inlet 112 to the production device 120 and discharged from the discharge outlet 113 through the pipe 115. The pump 118 is also operated to supply a raw solution stored in the raw solution tank 117 to the electrolysis device 100. Power is supplied to the electrolysis device 100 from a power supply (not illustrated) to electrolyze the raw solution. A high-concentration electrolyzed water produced by electrolysis is supplied to the pipe 115 and diluted with water flowing through the pipe 115 so as to have an appropriate concentration. The diluted electrolyzed water is fed to an electrolyzed water-supplying point through a pipe such as a hose that is suitably connected to the discharge outlet 113. When the switch 114 is turned OFF, the power supply to the solenoid-controlled valve 116, the pump 118, and the electrolysis device 100 is shut off and the operation is stopped.

There is also known an electrolytic cell for producing a hypochlorite which includes a plurality of bipolar unit electrolytic cells. In this electrolytic cell for producing a hypochlorite, a cooling room is disposed at an inlet from which an electrolysis solution flows in or an outlet from which an electrolysis solution is discharged in each of the unit electrolytic cells (refer to PTL 1). In this method, a decrease in the effective electrode area can be prevented, the decrease being caused by accumulation of generated air bubbles rising to an upper portion of the electrolysis unit and thus by no immersion of an upper portion of the electrode with an electrolysis solution. The electrolysis device (referred to as an electrolytic cell in PTL 1) in PTL 1 includes a plurality of electrode plates arranged in a direction perpendicular to a horizontal plane, and a liquid to be treated is supplied from the lower side to the upper side.

There is also known a fused-salt electrolytic cell in which an anode and a cathode are disposed in an electrolytic cell in an inclined manner, and chlorine gas produced is moved upward and zinc produced is moved downward (refer to PTL 2).

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 6-200393

PTL 2: Japanese Unexamined Patent Application Publication No. 2003-328173

SUMMARY OF INVENTION Technical Problem

However, such a known electrolysis device poses a problem in that the production efficiency of an electrolysis product is not sufficiently high.

In view of the foregoing, the present invention provides an electrolysis device capable of efficiently producing an electrolysis product.

Solution to Problem

The present invention provides an electrolysis device including an electrolysis unit. The electrolysis unit includes a channel for fluid to be treated, at least one electrolysis electrode pair, a flow inlet, and a flow outlet. The electrolysis electrode pair is disposed so as to incline with respect to a vertical direction and includes an upper electrode and a lower electrode disposed so as to face each other. The channel for fluid to be treated is disposed so that a fluid that has flowed in from the flow inlet flows through an interelectrode channel between the upper electrode and the lower electrode from a lower side to an upper side and flows out from the flow outlet.

Advantageous Effects of Invention

According to the present invention, the electrolysis device includes an electrolysis unit; the electrolysis unit includes a channel for fluid to be treated, at least one electrolysis electrode pair, a flow inlet, and a flow outlet; the electrolysis electrode pair includes an upper electrode and a lower electrode disposed so as to face each other; and the channel for fluid to be treated is disposed so that a fluid that has flowed in from the flow inlet flows through an interelectrode channel between the upper electrode and the lower electrode and flows out from the flow outlet. Therefore, when the fluid is caused to flow through the channel for fluid to be treated and a voltage is applied to the electrolysis electrode pair, the fluid is electrolyzed to produce an electrolysis product, and such a fluid containing an electrolysis product can be continuously produced.

According to the present invention, the electrolysis electrode pair is disposed so as to incline with respect to a vertical direction and the channel for fluid to be treated is disposed so that a fluid flows through an interelectrode channel from a lower side to an upper side. Therefore, an electrolysis product can be efficiently produced. This has been demonstrated from an experiment conducted by the present inventors and the like.

The reason for which an electrolysis product can be efficiently produced is believed to be as follows.

In the electrolysis device of the present invention, gas is generated through an electrode reaction at the lower electrode and thus air bubbles are generated on the lower electrode. The air bubbles can be caused to float toward the upper electrode so as to cross a fluid flowing in the flow direction. As a result of a flow of the fluid caused by the floating of the air bubbles, a fluid around the lower electrode and a fluid around the upper electrode can be stirred and mixed, which facilitates the electrode reaction at the upper electrode. Furthermore, the movement of a fluid located upstream of the lower electrode in the direction toward the upper electrode is facilitated with the movement of the air bubbles. Therefore, a fluid located downstream of the lower electrode contains a small fraction of a liquid component subjected to electrolysis. Thus, the production efficiency of an electrolysis product can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(a) and 1(b) are schematic sectional views of an electrolysis device according to an embodiment of the present invention. FIG. 1(c) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device is viewed in a vertical direction A. FIG. 1(d) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device is viewed in a direction B perpendicular to a principal surface of the lower electrode.

FIGS. 2(a) and 2(b) are schematic sectional views of an electrolysis device according to an embodiment of the present invention. FIG. 2(c) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device is viewed in a vertical direction A. FIG. 2(d) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device is viewed in a direction B perpendicular to a principal surface of the lower electrode.

FIG. 3(a) is a schematic sectional view of an electrolysis device according to an embodiment of the present invention. FIG. 3(b) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device is viewed in a vertical direction A. FIG. 3(c) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device is viewed in a direction B perpendicular to a principal surface of the lower electrode.

FIG. 4 is a schematic sectional view of an electrolysis device according to an embodiment of the present invention.

FIG. 5 is a schematic sectional view of an electrolysis device produced in an electrolysis experiment.

FIG. 6(a) is a schematic sectional view of an electrolysis device according to an embodiment of the present invention. FIGS. 6(b) to 6(d) are schematic sectional views of constituent parts of the electrolysis device.

FIGS. 7(a) and 7(b) are schematic sectional views of an electrolysis device according to an embodiment of the present invention.

FIG. 8 is a schematic sectional view of an electrolysis device according to an embodiment of the present invention.

FIG. 9(a) is a schematic sectional view of an electrolysis device according to an embodiment of the present invention. FIGS. 9(b) to 9(f) are schematic sectional views of constituent parts of the electrolysis device.

FIGS. 10(a) and 10(b) are schematic views of electrolysis devices according to an embodiment of the present invention.

FIG. 11 is a schematic view of an electrolysis device according to an embodiment of the present invention.

FIG. 12 is a graph showing the measurement result of an electrolysis experiment.

FIG. 13 is a diagram for describing flows of a fluid and air bubbles in an interelectrode channel.

FIGS. 14(a) to 14(c) are schematic sectional views of electrolysis devices produced in an electrolysis experiment.

FIGS. 15(a) and 15(b) are schematic sectional views of a known electrolysis device.

FIG. 16 is a schematic perspective view of a known electrolyzed water-producing device.

FIG. 17 schematically illustrates the internal structure of the known electrolyzed water-producing device.

FIG. 18 is a graph showing the measurement result of an electrolysis experiment.

FIG. 19 is a schematic view of an electrolysis device produced in an electrolysis experiment.

FIGS. 20(a) to 20(c) are schematic sectional views of electrolysis devices according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

An electrolysis device of the present invention includes an electrolysis unit. The electrolysis unit includes a channel for fluid to be treated, at least one electrolysis electrode pair, a flow inlet, and a flow outlet. The electrolysis electrode pair is disposed so as to incline with respect to a vertical direction and includes an upper electrode and a lower electrode disposed so as to face each other. The channel for fluid to be treated is disposed so that a fluid that has flowed in from the flow inlet flows through an interelectrode channel between the upper electrode and the lower electrode from a lower side to an upper side and flows out from the flow outlet.

In the electrolysis device of the present invention, the electrolysis electrode pair is preferably disposed so as to have an inclination angle of more than 0° and less than 50° with respect to the vertical direction.

In this configuration, the electrolysis efficiency of the electrolysis unit can be improved. This has been demonstrated from an electrolysis experiment conducted by the present inventors and the like.

In the electrolysis device of the present invention, the channel for fluid to be treated preferably includes an upstream-side bent channel located close to an end of the interelectrode channel on an upstream side or a downstream-side bent channel located close to an end of the interelectrode channel on a downstream side.

When the channel for fluid to be treated includes an upstream-side bent channel or a downstream-side bent channel, gas generated through an electrolysis reaction can be efficiently discharged from the interelectrode channel, and therefore a decrease in electrolysis efficiency due to holding of gas can be suppressed.

Furthermore, when the channel for fluid to be treated includes an upstream-side bent channel, a turbulent flow can be caused on a liquid in the channel for fluid to be treated. By disposing the bent channel near the electrode, the influence of the turbulent flow generated in the bent channel is exerted on the interelectrode channel. This sufficiently produces a stirring effect from near the inlet of the interelectrode channel where air bubbles are not so generated. Therefore, the diffusion of a substance near the electrode surface can be facilitated, and the electrolysis efficiency can be improved.

In the case where the channel for fluid to be treated includes a downstream-side bent channel, even if there is a gas not sufficiently dissolved at the interelectrode channel, stirring can be performed again at the bent channel. For example, when an aqueous solution of a substance containing a chlorine atom is electrolyzed to produce hypochlorous acid, chlorine gas is not sufficiently dissolved in the aqueous solution under some conditions, which sometimes decreases the production efficiency of hypochlorous acid. In this configuration, however, the dissolution of chlorine gas in the aqueous solution and the conversion into hypochlorous acid can be facilitated, and the electrolysis efficiency can be substantially improved.

In the electrolysis device of the present invention, the upper electrode preferably serves as an anode, and the lower electrode preferably serves as a cathode.

In this configuration, air bubbles can be generated through a cathodic reaction at the lower electrode, and the electrolysis efficiency can be improved by a stirring and mixing effect produced by the air bubbles.

In the electrolysis device of the present invention, the lower electrode preferably has an electrode surface area larger than that of the upper electrode.

In the case where an aqueous solution of a substance containing a chlorine atom is electrolyzed to produce hypochlorous acid using the lower electrode as a cathode and the upper electrode as an anode, if the electrode surface of the upper electrode and the electrode surface of the lower electrode have substantially the same area, air bubbles of chlorine gas are dissolved and reduced around the upper electrode by a stirring and mixing effect produced by air bubbles and thus a decrease in the effective electrode area due to the air bubbles is suppressed. However, such an effect is not produced at the lower electrode, and the effective electrode area is sometimes decreased by air bubbles of hydrogen gas. This relatively decreases the effective electrode area of the lower electrode, which is a rate-determining factor of the electrolysis reaction. Consequently, the area of the upper electrode is sometimes not effectively utilized.

By increasing the electrode surface area of the lower electrode more than the upper electrode, the above phenomenon can be relaxed. Consequently, the electrode surface area can be effectively utilized, and the electrolysis efficiency per unit area of the upper electrode can be improved.

In the above configuration, when air bubbles of hydrogen gas generated on the upstream side of the lower electrode come close to the upper electrode serving as an anode and located above the lower electrode in the vertical direction, the air bubbles can be brought into contact with an aqueous solution which has been electrolyzed on the upstream side of the upper electrode and thus whose pH has been decreased. Therefore, chlorine gas can be efficiently converted into hypochlorous acid.

In the above configuration, even if hydrogen gas generated at the lower electrode floats on the downstream side with respect to the vertically upward direction by the velocity of flow of a liquid, the hydrogen gas comes close to the upper electrode. This increases the fraction of chlorine gas converted into hypochlorous acid. In particular, even if an electric field on the downstream side of the upper electrode is shielded by a large amount of air bubbles of hydrogen gas generated, the fraction of chlorine gas converted into hypochlorous acid can be expected to be increased to some degree by a fringing field to the electrode that extends to the downstream side or oxidation of air bubbles that have directly contacted the electrode.

The electrolysis device of the present invention preferably further includes a dilution unit. In the electrolysis device, preferably, the fluid is an aqueous solution, the electrolysis electrode pair is disposed so that a hypochlorite ion is electrochemically produced from a chlorine-containing compound contained in the aqueous solution, the aqueous solution at the flow outlet contains 4000 ppm or more of a hypochlorite ion on a weight basis, the dilution unit is disposed so as to produce a diluted solution of the aqueous solution that contains a hypochlorite ion and is discharged from the flow outlet, and the diluted solution has a pH of 7.5 or less.

In this configuration, an electrolyzed water that contains a hypochlorite ion and has a pH of 7.5 or less can be efficiently produced by electrolysis while the release of chlorine gas is suppressed.

In the electrolysis device of the present invention, preferably, the electrolysis unit is disposed so that a hypochlorite ion is electrochemically produced from the chlorine-containing compound, the upper electrode serves as an anode, and the lower electrode serves as a cathode.

In this configuration, air bubbles of hydrogen gas generated through a cathodic reaction at the lower electrode move to near the upper electrode so as to cross a fluid flowing in the flow velocity direction. Therefore, stirring of a liquid near the anode and a liquid near the cathode can be facilitated in the electrolysis unit. Furthermore, alkaline water near the cathode is carried to near the anode with the movement of air bubbles of hydrogen gas to near the anode, and chlorine gas generated through an anodic reaction is brought into contact with an alkalescent aqueous solution. Thus, the conversation of chlorine gas into hypochlorous acid or the like can be facilitated.

In the electrolysis device of the present invention, when the cross section of the electrolysis unit in a direction in which the cross-sectional area of the interelectrode channel is the smallest includes a plane C that includes the upper electrode, but does not include the lower electrode, a plane D that includes both the upper electrode and the lower electrode, and a plane E that includes the lower electrode, but does not include the upper electrode, the upper electrode and the lower electrode are preferably disposed so that the plane C is located at the top, the plane E is located at the bottom, and the plane D is located between the plane C and the plane E.

In this configuration, even if air bubbles generated at the lower electrode are carried away toward the flow outlet with respect to the vertically upward direction by the flow velocity, the air bubbles can be brought close to the upper electrode. For example, in the case where an aqueous solution of a substance containing a chlorine atom is electrolyzed to produce hypochlorous acid, even if hydrogen gas generated on the downstream side of the lower electrode floats on the downstream side with respect to the vertically upward direction by the velocity of flow of a liquid, the hydrogen gas can be brought close to the upper electrode serving as an anode. This increases the fraction of chlorine gas converted into hypochlorous acid.

In the electrolysis device of the present invention, the upper electrode is preferably curved so as to have a projected shape facing the lower electrode and the lower electrode is preferably curved so as to have a depressed shape facing the upper electrode. The radius of curvature of the upper electrode is preferably smaller than that of the lower electrode.

In this configuration, air bubbles of chlorine gas or the like generated at the upper electrode serving as an anode can be discharged from the center to the end of the electrode. This suppresses a decrease in the effective electrode area due to the air bubbles and also improves the electrolysis efficiency at the center. Furthermore, air bubbles of hydrogen gas or the like generated at the lower electrode serving as a cathode smoothly move to near the upper electrode without being interrupted by air bubbles of chlorine gas or the like. This increases a stirring and mixing effect produced by air bubbles generated at the lower electrode. When hypochlorous acid is produced by electrolysis, the stirring and mixing effect produced by the air bubbles facilities the conversion of chlorine gas into hypochlorous acid. Consequently, the amount of air bubbles of chlorine gas can be decreased, which further suppresses a decrease in the effective electrode area and further improves the electrolysis efficiency.

The movement of the air bubbles from the center to the end of the upper electrode generates a flow velocity vector in the direction from the center to the end. This increases the flow velocity at the center and decreases the flow velocity at the end compared with known electrode unit structures. Consequently, the variation in the degree of electrolysis between an electrolysis solution flowing at the center and an electrolysis solution flowing at the end can be suppressed.

Furthermore, the amount of air bubbles at the center of the upper electrode can be made smaller than that at the end of the upper electrode. Therefore, the electrolysis efficiency is increased at the center where the flow velocity tends to be relatively high. Consequently, the variation in the degree of electrolysis between an electrolysis solution flowing at the center and an electrolysis solution flowing at the end can be further suppressed.

In the electrolysis device of the present invention, at least part of the upper electrode is preferably a mesh-like electrode, and a space is preferably provided on the side (hereafter, back side) of the upper electrode opposite to the lower electrode. The electrolysis device of the present invention also preferably includes an electrode electrically connected to the upper electrode and disposed on at least part of a wall surface that defines the space.

In this configuration, air bubbles on the upper electrode can be discharged to the back side. This suppresses a decrease in the effective electrode area caused by covering the surface of the upper electrode facing the lower electrode with air bubbles and thus improves the electrolysis efficiency. When hypochlorous acid is produced by electrolysis, air bubbles of hydrogen gas that have risen from the lower electrode are less likely to be interrupted by air bubbles of chlorine gas and can be easily brought into contact with an aqueous solution generated near the upper electrode and having a relatively high pH. Therefore, the chlorine gas can be efficiently converted into hypochlorous acid. In the above configuration, electrolysis can also be performed at the electrode disposed on the wall surface through openings of the mesh. This further increases the effective electrode area.

In the electrolysis device of the present invention, the lower electrode is preferably a mesh-like electrode.

In this configuration, some of air bubbles generated on the surface of the lower electrode are believed to grow so as to cover openings of the mesh when viewed from the upper electrode. This decreases the ratio of an electrode surface area that is ineffective because of coverage with air bubbles compared with the case of an electrode having a smooth electrode surface.

When at least one of the upper electrode and the lower electrode is a mesh-like electrode, the irregularities of the electrode surface increase, which makes it difficult to form laminar flows in the interelectrode channel. Consequently, vortex flows and turbulent flows are easily formed in the interelectrode channel, which facilitates the separation of air bubbles from the electrode. When hypochlorous acid is produced by electrolysis, minute air bubbles of chlorine gas having a large specific surface area before the air bubbles grow to large air bubbles are separated from the electrode and can be brought into contact with an aqueous solution having a relatively low pH near the upper electrode. Therefore, the chlorine gas is quickly dissolved and converted into hypochlorous acid. The stirring of the electrolysis solution is also facilitated, and thus the dissolution of chlorine gas and the conversion into hypochlorous acid in the electrolysis unit are efficiently performed.

In the electrolysis device of the present invention, an air bubble guide is preferably disposed between the upper electrode and the lower electrode. The air bubble guide is a plate-shaped member disposed away from the upper electrode and the lower electrode. The plate-shaped member is preferably disposed so as to incline with respect to a direction parallel to the upper electrode and the lower electrode. The plate-shaped member is preferably disposed so as to be substantially perpendicular to the upper electrode and the lower electrode.

In this configuration, some of air bubbles generated on the surface of the lower electrode rise to about the middle, and then the path of the air bubbles is directly changed by the air bubble guide or is indirectly changed following a liquid flow changed by the air bubble guide. This complicates the paths of the air bubbles compared with the case of no air bubble guide. Furthermore, an electrolysis solution is stirred by turbulent flows generated on the rear side of the air bubble guide. The coalescence of air bubbles can also be suppressed by the air bubble guide, which increases the solubility of air bubbles. This increases the probability that air bubbles generated at the lower electrode are brought into contact with a liquid subjected to electrolysis near the upper electrode compared with the case of no air bubble guide. In addition to the air bubbles, an electrolyzed water near the upper electrode or the lower electrode is also affected by turbulent flows generated by the air bubble guide. Thus, the electrolyzed water near the upper electrode or the lower electrode is also stirred in addition to the air bubbles. This considerably improves the diffusion controlling in the electrolysis reaction and also facilities the dissolution of air bubbles because of mixing and stirring of air bubbles. Consequently, the electrolysis reaction is facilitated overall and thus the electrolysis efficiency is improved.

In the electrolysis device of the present invention, preferably, the air bubble guide is a columnar member disposed away from the upper electrode and the lower electrode, and the axis of the column of the member is substantially parallel to the upper electrode and the lower electrode.

In this configuration, the movement of air bubbles and the flow of a liquid can be prevented from being interrupted more than necessary. Furthermore, a stirring effect can be produced on the air bubbles and liquid while a decrease in the effective electrode area is minimized.

In the electrolysis device of the present invention, preferably, the electrolysis unit includes a first electrode holder to which the lower electrode is fixed, a second electrode holder to which the upper electrode is fixed, and a spacer disposed between the first and second electrode holders, and the spacer is disposed so that at least part of the spacer overlaps the upper electrode and the lower electrode when viewed in a direction in which the upper electrode and the lower electrode overlap each other. More preferably, the first or second electrode holder at least has a recess to which the electrode is to be fixed, and the distance (the depth of the recess) between the surface to which the electrode is fixed and the surface of the spacer is larger than the thickness of the electrode to be fixed.

In this configuration, a stirring effect can be produced on air bubbles and a liquid. Even if the electrode is warped or loosened for some reason, the probability that both the electrodes are brought into contact with each other can be decreased. This improves both the efficiency and safety of the electrolysis device. Furthermore, the distance between the electrodes can be easily changed by changing the thickness of the spacer. Therefore, the specifications can be easily changed in accordance with the purposes of products, and thus commonality of parts such as an electrode holder is easily achieved.

In the electrolysis device of the present invention, preferably, a protrusion is disposed that protrudes from a surface parallel to a part of the channel for fluid to be treated and the surface of the upper electrode or lower electrode, and at least part of the protrusion is disposed on a symmetry plane in a structure that defines the channel for fluid to be treated.

In a known structure, the flow velocity is relatively high around the center of the interelectrode channel, that is, around the center of the electrode, and thus the time for which an electrolysis solution flowing through the center is electrolyzed is shortened. The flow velocity is relatively low at the end, and thus the time for which an electrolysis solution flowing through the end is electrolyzed is lengthened. Consequently, the electrolysis solution is not uniformly electrolyzed, which causes concentration unevenness.

When the electrolysis conditions are set to electrolysis conditions suitable for an electrolysis solution flowing through the center, an electrolysis solution flowing through the end is electrolyzed more than necessary from a certain position or is not electrolyzed at all, which makes the electrode area ineffective. When the electrolysis conditions are set to electrolysis conditions suitable for an electrolysis solution flowing through the end, the electrolysis solution flowing through the center is not sufficiently electrolyzed. Electrolysis is not efficiently performed in either case, but the presence of the protrusion decreases the flow velocity at the center and increases the flow velocity at the end in a very simple structure. Therefore, the occurrence of concentration unevenness can be suppressed and the electrolysis efficiency can be improved.

In the electrolysis device of the present invention, regarding the shape of the channel for fluid to be treated, when the upper electrode, the lower electrode, the flow inlet, the flow outlet, and the protrusion are projected in the direction of the normal to a cross-section taken along a plane parallel to the electrode surface of the upper electrode or lower electrode, the widths of the upper electrode and the lower electrode are preferably relatively large and the widths of the flow inlet, the flow outlet, and the protrusion are preferably relatively small.

In this configuration, the uniformity of the flow velocity can be improved. This suppresses the concentration unevenness and improves the electrolysis efficiency.

In the electrolysis device of the present invention, the channel for fluid to be treated is preferably disposed so that the cross-sectional area of a channel near the flow outlet is larger than that of the interelectrode channel.

In this configuration, the variation in the flow velocity near the flow outlet can be suppressed and also the air bubbles are easily discharged. For example, even if unconverted chlorine gas is generated in the production of hypochlorous acid, a stirring effect and a holding effect can be expected in a portion where the cross-sectional area of a channel is large. Thus, the conversation of chlorine gas into hypochlorous acid can be expected to be facilitated. Therefore, an improvement in the efficiency can be expected.

In the electrolysis device of the present invention, the protrusion is preferably disposed on each of the upstream side and downstream side of the interelectrode channel.

In the case where the size of the upper electrode and lower electrode is large particularly in the flow velocity direction, for example, when the protrusion is present on the upstream side and is not present on the downstream side, the flow velocity around the center tends to increase again on the downstream side and the flow velocity around the end tends to decrease. In such a case, the variation in the flow velocity can be suppressed by disposing the protrusion on both the upstream side and downstream side.

In the electrolysis device of the present invention, preferably, the electrolysis unit includes the upper and lower electrodes, electrode holders that define a channel other than the interelectrode channel, and the protrusion; at least part of the protrusion is connected to the upper electrode, the lower electrode, a base of these electrodes, or a member physically coupled with these electrodes; and the at least part of the protrusion is also connected to the electrode holders.

In this configuration, the upper electrode or the lower electrode can be fixed to the electrode holder by disposing the protrusion, and there is no need to separately fix the electrode. Therefore, the electrolysis device of the present invention can be provided without complicating the configuration and structure.

In the electrolysis device of the present invention, preferably, at least part of the protrusion or a member including the protrusion is made of a conductive material, and at least part of the member made of the conductive material is electrically connected to the upper electrode or the lower electrode.

In this configuration, the member made of the conductive material can be used for fixing the upper electrode or the lower electrode to the electrode holder and applying a voltage to the upper electrode or the lower electrode. Thus, a lead line for applying a voltage to the electrode is not additionally required. Therefore, the complication of the configuration and structure is prevented. Furthermore, there is no need to attach electrode terminal lead parts such as pins later unlike known electrolysis electrode pairs, which reduces the number of parts (pins) and the number of processes for attaching pins. Alternatively, the electrode terminal may be led by attaching a lug for terminals to the electrode in advance. However, when blanking is employed, some material is wasted. When a lug is attached later, a process for attaching a lug later needs to be performed. It is also difficult to use a cheap O-ring for sealing to prevent leakage of an electrolysis solution from a leading portion, but such a waste or process is not required in the present invention. Alternatively, there is a method for leading an electrode terminal to the back surface of the electrode, and a rod is welded to the back surface of the electrode in known electrodes. Although welding may also be employed in the present invention, the electrode can be fixed and the electrode terminal can be led without employing welding. Therefore, failure of welding does not occur because there is no welding process. Even if electrode terminal parts have defects, the parts can be easily repaired. If welding is employed, the weld is removed and a new rod is welded again or the electrode itself needs to be exchanged.

In the electrolysis device of the present invention, at least a portion of the surface of the protrusion closest to the counter electrode is preferably nonconductive.

In this configuration, proceeding of an electrochemical reaction on the surface of the protrusion can be suppressed.

In the electrolysis device of the present invention, preferably, the member including the protrusion is disposed so as to be parallel to the direction of the normal to main electrode surfaces that define the interelectrode channel, and the member connects the electrode holder and the electrode to each other.

Thus, the upper electrode or the lower electrode can be fixed to the electrode holder and a voltage can be applied to the upper electrode and the lower electrode by a very simple method.

In the electrolysis device of the present invention, preferably, the first electrode holder to which the lower electrode is fixed and the second electrode holder to which the upper electrode is fixed have substantially the same shape and are disposed symmetrically about a point; a spacer is disposed between the first and second electrode holders; and at least part of the spacer overlaps the upper electrode and the lower electrode when viewed in a direction in which the upper electrode and the lower electrode overlap each other.

In this configuration, even if the electrode is warped or loosened for some reason, the probability that both the electrodes are brought into contact with each other can be decreased. This improves the safety of the electrolysis device. Furthermore, the distance between the electrodes can be easily changed by changing the thickness of the spacer. Therefore, the specifications can be easily changed in accordance with the purposes of products, and thus commonality of parts such as an electrode holder is easily achieved.

In the electrolysis device of the present invention, the spacer preferably overlaps edges of the upper electrode and the lower electrode when viewed in a direction in which the upper electrode and the lower electrode overlap each other.

In this configuration, the electrolysis at electrode edges where an electric field is easily concentrated and degradation is easily caused can be suppressed. This stabilizes the electrolysis, suppresses the electrode wear, and increases the life.

In the electrolysis device of the present invention, the electrolysis unit is preferably disposed so that an aqueous solution of a compound containing a chlorine atom is electrolyzed to produce at least one of a hypochlorite ion and a chlorine molecule having a concentration corresponding to 4000 ppm or more, and the at least one of a hypochlorite ion and a chlorine molecule is diluted to produce a hypochlorous acid water having a pH of 7 or less.

In this case, the production efficiency of the hypochlorous acid water can be improved by employing the above means.

Hereafter, embodiments of the present invention will be described with reference to the attached drawings. The configurations in the drawings and the following description are merely examples, and the scope of the present invention is not limited by the drawings and the following description.

First Embodiment

FIGS. 1(a) and 1(b) are schematic sectional views of an electrolysis device according to the first embodiment. FIG. 1(c) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device in FIG. 1(a) is viewed in a vertical direction A. FIG. 1(d) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device in FIG. 1(a) is viewed in a direction B perpendicular to a principal surface of the lower electrode.

An electrolysis device 15 according to the first embodiment includes an electrolysis unit 10. The electrolysis unit 10 includes a channel 7 for fluid to be treated, at least one electrolysis electrode pair 5, a flow inlet 8, and a flow outlet 9. The electrolysis electrode pair 5 is disposed so as to incline with respect to the vertical direction, includes an upper electrode 3 and a lower electrode 4 disposed so as to face each other, and is disposed so that an electrode reaction that generates a gas proceeds at the lower electrode 4. The channel 7 for fluid to be treated is disposed so that a fluid that has flowed in from the flow inlet 8 flows through an interelectrode channel 6 between the upper electrode 3 and the lower electrode 4 from the lower side to the upper side and flows out from the flow outlet 9.

In the electrolysis device 15 (electrolysis unit 10) according to the first embodiment, the plate-shaped upper electrode 3 and the plate-shaped lower electrode 4 are fixed to a casing 1 so as to face each other, and the interelectrode channel 6 is formed between the upper electrode 3 and the lower electrode 4. When the electrolysis electrode pair 5 is disposed so as to incline with respect to the vertical direction, the upper electrode 3 is an electrode located on the upper side and the lower electrode 4 is an electrode located on the lower side.

The electrolysis unit 10 is a unit including the channel 7 for fluid to be treated and is a constituent unit of the electrolysis device 15. The electrolysis device 15 is constituted by a single electrolysis unit 10 in FIG. 1, but the electrolysis device 15 may be constituted by a plurality of electrolysis units 10. The plurality of electrolysis units 10 may be combined with each other so that the channels 7 for fluid to be treated are arranged in parallel or in series.

The casing 1 is provided so that the channel 7 for fluid to be treated can be formed by the casing 1, the upper electrode 3, and the lower electrode 4. The casing 1 is made of a material having resistance to a fluid that flows through the channel 7 for fluid to be treated and a gas generated by electrolysis as a by-product. Specific examples of the material for the casing 1 include fluorocarbon resins, vinyl chloride resins, polypropylene resins, and acrylic resins in consideration of durability.

The casing 1 may have a tubular structure or may have a structure in which the channel 7 for fluid to be treated is formed by combining a plurality of members. When the casing 1 has a tubular structure, the upper electrode 3 and the lower electrode 4 can be fixed onto the inner wall surface of the tubular structure. When the casing 1 has a structure including a plurality of members combined with each other, the channel 7 for fluid to be treated may be formed by combining a first member to which the upper electrode 3 is fixed and a second member to which the lower electrode 4 is fixed. In this case, a third member may be sandwiched between the first member and the second member. The member for the casing 1 or the casing 1 may be an electrode holder to which the upper electrode 3 or the lower electrode 4 is fixed.

The channel 7 for fluid to be treated is disposed so that a fluid that has flowed in from the flow inlet 8 flows through the interelectrode channel 6 between the upper electrode 3 and the lower electrode 4 from the lower side to the upper side and flows out from the flow outlet 9. The flow inlet 8 can be connected to a raw electrolysis solution tank via a pump. Thus, the raw electrolysis solution in the tank can be caused to flow through the channel 7 for fluid to be treated and electrolysis can be performed. The flow outlet 9 can be connected to, for example, a tank for storing a fluid subjected to electrolysis, a liquid-feeding pipe through which a fluid subjected to electrolysis is fed to a place where the fluid is used, or a dilution unit.

As a result of the flow of a fluid from the lower side to the upper side of the interelectrode channel 6, gas generated at the upper electrode 3 or the lower electrode 4 can be efficiently discharged from the interelectrode channel 6, which suppresses a decrease in electrolysis efficiency due to holding of the gas. Furthermore, the flow inlet 8 can be disposed below a lower edge of the interelectrode channel 6 and the flow outlet 9 can be disposed above an upper edge of the interelectrode channel 6. Thus, gas generated at the upper electrode 3 or the lower electrode 4 can be efficiently discharged from the interelectrode channel 6, which suppresses a decrease in electrolysis efficiency due to holding of the gas.

The channel 7 for fluid to be treated is constituted by a part of the casing 1 and the interelectrode channel 6. The inner wall surface of the channel 7 for fluid to be treated is desirably constituted by an electrolysis electrode pair 5 having as large a surface as possible and a casing 1 having as small a surface as possible. In this configuration, the electrode surface area which is included in the inner wall surface of the channel 7 for fluid to be treated and in which an electrolysis reaction proceeds can be increased, and a surface area that does not contribute to electrolysis can be decreased as much as possible. By increasing the electrode surface area, an electrolysis reaction can be sufficiently caused to proceed at a low current density. Therefore, the life of the electrolysis electrode pair 5 can be extended and the electrolysis efficiency can also be improved. By decreasing the surface area that does not contribute to electrolysis, the internal volume of the electrolysis unit 10 can be decreased while the same electrolysis performance is maintained. Therefore, the startup characteristics of the electrolysis device 15 can be improved. When electrolyzed water is produced using the electrolysis device 15, the rise of the concentration of the electrolyzed water can be improved.

The electrolysis electrode pair 5 includes the upper electrode 3 and the lower electrode 4. The electrolysis unit 10 in FIG. 1 includes one electrolysis electrode pair 5, but may include a plurality of electrolysis electrode pairs 5.

The upper electrode 3 and the lower electrode 4 are disposed so that the principal surface (electrode surface) of the upper electrode 3 and the principal surface (electrode surface) of the lower electrode 4 face each other. The upper electrode 3 and the lower electrode 4 are also disposed so that the interelectrode channel 6 is formed between the principal surface of the upper electrode 3 and the principal surface of the lower electrode 4. Furthermore, the upper electrode 3 and the lower electrode 4 can be disposed so that the principal surface of the upper electrode 3 and the principal surface of the lower electrode 4 are substantially parallel to each other. The interelectrode channel 6 is a part of the channel 7 for fluid to be treated. In this configuration, a fluid flowing through the interelectrode channel 6 can be electrolyzed by applying a voltage between the upper electrode 3 and the lower electrode 4, and thus a fluid containing an electrolysis product can be produced.

The upper electrode 3 may be curved so as to have a projected shape facing the lower electrode 4 and the lower electrode 4 may be curved so as to have a depressed shape facing the upper electrode 3. The radius of curvature of the upper electrode 3 may be smaller than that of the lower electrode 4.

The upper electrode 3 and the lower electrode 4 are each connected to a wiring line for applying a potential difference between the electrodes, and the wiring lines are connected to a power supply. The wiring line may be a conductive member used for fixing the upper electrode 3 or the lower electrode 4 to the casing 1.

The upper electrode 3 and the lower electrode 4 may be disposed so that the upper electrode 3 serves as an anode and the lower electrode 4 serves as a cathode or so that the upper electrode 3 serves as a cathode and the lower electrode 4 serves as an anode.

The upper electrode 3 and the lower electrode 4 are disposed so that an electrode reaction that generates gas proceeds at the lower electrode 4. This efficiently produces an electrolysis product. If an electrode reaction that generates gas proceeds at both the upper electrode 3 and the lower electrode 4, the upper electrode 3 and the lower electrode 4 can be disposed so that the amount of air bubbles generated is larger at the lower electrode 4 than at the upper electrode 3.

The upper electrode 3 and the lower electrode 4 can be fixed to the casing 1. The upper electrode 3 or the lower electrode 4 may be fixed to the casing 1 with a screw member or may be fixed to the casing 1 with an adhesive. The upper electrode 3 or the lower electrode 4 may be fixed to a flat surface or a curved surface of the casing 1 or may be fixed to a groove of the casing 1. In the electrolysis device 10 in FIG. 1, the upper electrode 3 and the lower electrode 4 are disposed in grooves of the casing 1 to prevent formation of steps in the channel 7 for fluid to be treated.

The upper electrode 3 and the lower electrode 4 may have a flat plate shape or a curved plate shape. The upper electrode 3 and the lower electrode 4 may have a rectangular shape or a circular shape. The upper electrode 3 and the lower electrode 4 may have substantially the same shape or different shapes. The upper electrode 3 and the lower electrode 4 included in the electrolysis unit 10 in FIG. 1 have substantially the same rectangular plate shape. The upper electrode 3 and the lower electrode 4 each have, for example, 8-cm long sides and 3-cm short sides.

The upper electrode 3 and the lower electrode 4 may have a mesh-like structure, a perforated structure, or a porous structure.

When at least part of the upper electrode 3 has a mesh-like structure or a perforated structure, a space may be provided on the side (back side) of the upper electrode 3 opposite to the lower electrode 4. Furthermore, a supporting electrode electrically connected to the upper electrode 3 may be disposed on a wall surface that defines the space. Thus, air bubbles on the electrode surface of the upper electrode 3 can be discharged to the back side, and therefore a decrease in the effective electrode area can be suppressed. Moreover, an electrode reaction can be caused to proceed on the supporting electrode, which increases the effective electrode area.

The upper electrode 3 and the lower electrode 4 is formed of a conductive material such as a metal material. The upper electrode 3 and the lower electrode 4 may be insoluble electrodes. The upper electrode 3 and the lower electrode 4 may each have a surface on which a catalyst such as Pt, Pd, Ir, or Ru is supported or coated. Thus, an electrolysis reaction can be efficiently caused to proceed.

For example, one of the upper electrode 3 and the lower electrode 4 serving as a cathode may be an electrode containing Ti, Pt, or another metal, and the other of the upper electrode 3 and the lower electrode 4 serving as an anode may be an electrode containing Ir or Ru or an insoluble electrode containing Pt or the like.

The upper electrode 3 and the lower electrode 4 (the electrolysis electrode pair 5) are disposed so as to incline with respect to the vertical direction. The upper electrode 3 and the lower electrode 4 are disposed so that at least part of the upper electrode 3 is located above the lower electrode 4 in the vertical direction.

The upper electrode 3 and the lower electrode 4 can be disposed so as to have an inclination angle of more than 0° and less than 50° with respect to the vertical direction. The inclination angle may be 5° or more and 45° or less and may also be 15° or more and 32° or less. The inclination angle is an inclination angle of a surface (principal surface or electrode surface) of the upper electrode 3 that faces the lower electrode 4 or an inclination angle of a surface (principal surface or electrode surface) of the lower electrode 4 that faces the upper electrode 3. The inclination angle of the upper electrode 3 and the inclination angle of the lower electrode 4 are preferably substantially the same. Thus, the distance between the electrodes can be substantially made constant, which suppresses the concentration of electric current.

By disposing the electrolysis electrode pair 5 in such a manner, the electrolysis efficiency can be improved.

In the electrolysis unit 10 in FIG. 1, the upper electrode 3 and the lower electrode 4 are disposed so as to have an inclination angle θ. As illustrated in FIG. 1(d), when viewed in a direction B perpendicular to the principal surface of the lower electrode 4, the upper electrode 3 and the lower electrode 4 having substantially the same size are disposed so that substantially the entire surfaces of the upper electrode 3 and the lower electrode 4 overlap each other. As illustrated in FIG. 1(c), when viewed in the vertical direction A, the upper electrode 3 and the lower electrode 4 are disposed so as to overlap each other in an overlap region 16. The electrolysis unit 10 is disposed so that a fluid to be treated flows from the lower side to the upper side of the interelectrode channel 6 and an electrode reaction that generates gas (air bubbles 11) proceeds at the lower electrode 4.

In this electrolysis unit 10, as illustrated in FIG. 1(b), air bubbles 11 are generated on the lower electrode 4 through the electrode reaction at the lower electrode 4. The air bubbles 11 can be caused to float toward the upper electrode 3 so as to cross a fluid flowing in the flow direction. As a result of a flow of the fluid caused by the floating of the air bubbles 11, a fluid around the lower electrode 4 and a fluid around the upper electrode 3 can be stirred and mixed, which facilitates the electrode reaction at the upper electrode 3. Furthermore, the movement of a fluid located upstream of the lower electrode 4 in the direction toward the upper electrode 3 is facilitated with the movement of the air bubbles 11. Therefore, a fluid located downstream of the lower electrode 4 contains a small fraction of a liquid component subjected to electrolysis. Thus, the production efficiency of an electrolysis product can be improved.

The electrolysis product produced by the electrolysis electrode pair 5 is, for example, hypochlorous acid. In this case, when an aqueous solution of an alkali metal chloride is supplied to the channel 7 for fluid to be treated (interelectrode channel 6) from the flow inlet 8 and a voltage is applied between the upper electrode 3 and the lower electrode 4, an electrolysis reaction represented by the above reaction formulae (1) to (4) can be caused to proceed, and thus an aqueous hypochlorite solution (electrolyzed water) can be produced.

Also in this case, a voltage can be applied so that the upper electrode 3 serves as an anode and the lower electrode 4 serves as a cathode. Consequently, air bubbles of H₂ gas can be generated on the lower electrode 4, the aqueous solution can be stirred and mixed by the floating of the air bubbles, and the production efficiency of hypochlorous acid can be improved. Furthermore, an aqueous solution near the anode can be prevented from becoming a strongly acidic solution. This increases the rate of reaction in the above reaction formula (2). Thus, the production efficiency of hypochlorous acid can be improved.

Second Embodiment

FIGS. 2(a) and 2(b) are schematic sectional views of an electrolysis device according to the second embodiment. FIG. 2(c) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device in FIG. 2(a) is viewed in a vertical direction A. FIG. 2(d) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device in FIG. 2(a) is viewed in a direction B perpendicular to a principal surface of the lower electrode.

In the electrolysis device in FIG. 1, the upper electrode 3 and the lower electrode 4 are disposed so that substantially the entire surfaces of the upper electrode 3 and the lower electrode 4 overlap each other when viewed in the direction B. However, in the electrolysis device 15 according to the second embodiment, the upper electrode 3 is disposed so as to shift upward. Specifically, as illustrated in FIG. 2(d), when viewed in the direction B perpendicular to the principal surface of the lower electrode 4, the upper electrode 3 and the lower electrode 4 overlap each other in an overlap region 17. However, an upper region included in the upper electrode 3 does not overlap the lower electrode 4, and a lower region included in the lower electrode 4 does not overlap the upper electrode 3.

In the electrolysis device 15 according to the second embodiment, when the cross section of the electrolysis unit 10 in a direction in which the cross-sectional area of the interelectrode channel 6 is the smallest includes a plane C that includes the upper electrode 3, but does not include the lower electrode 4, a plane D that includes both the upper electrode 3 and the lower electrode 4, and a plane E that includes the lower electrode, but does not include the upper electrode 3, the upper electrode 3 and the lower electrode 4 are disposed so that the plane C is located at the top, the plane E is located at the bottom, and the plane D is located between the plane C and the plane E.

In this configuration, as illustrated in FIG. 2(c), the overlap region 16 where the upper electrode 3 and the lower electrode 4 overlap each other when viewed in the vertical direction A can be widened.

In this electrolysis unit 10, as illustrated in FIG. 2(b), air bubbles 11 are generated through the electrode reaction at the lower electrode 4, and the air bubbles 11 can be caused to float toward the upper electrode 3 so as to cross a fluid flowing in the flow direction. Furthermore, since the overlap region 16 is large as illustrated in FIG. 2(c), the probability that the air bubbles 11 generated at the lower electrode 4 float and come close to the upper electrode 3 can be increased. Furthermore, even if the air bubbles 11 generated at the lower electrode 4 are carried away downstream by the flow in the channel 7 for fluid to be treated, the air bubbles 11 can be brought close to the upper electrode 3 with a high probability. Therefore, a stirring and mixing effect produced by the air bubbles 11 can be increased, and the electrode reaction at the upper electrode 3 can be more effectively facilitated. Thus, the production efficiency of an electrolysis product can be improved.

For example, in the case where an aqueous solution of a substance containing a chlorine atom is electrolyzed to produce hypochlorous acid with the electrolysis device 15 according to the second embodiment using the lower electrode 4 as an anode and the upper electrode 3 as a cathode, even if chlorine gas generated at the lower electrode 4 floats on the downstream side with respect to the vertically upward direction by the velocity of flow of a liquid, the chlorine gas can be brought close to the upper electrode 3 serving as a cathode. This increases the fraction of chlorine gas converted into hypochlorous acid.

Third Embodiment

FIG. 3(a) is a schematic sectional view of an electrolysis device according to the third embodiment. FIG. 3(b) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device in FIG. 3(a) is viewed in a vertical direction A. FIG. 3(c) is a diagram for describing an overlap of an upper electrode and a lower electrode when the electrolysis device in FIG. 3(a) is viewed in a direction B perpendicular to an electrode surface of the lower electrode.

In the electrolysis devices 15 illustrated in FIGS. 1 and 2, the electrode surface of the upper electrode 3 and the electrode surface of the lower electrode 4 have substantially the same size. However, in the electrolysis device 15 according to the third embodiment, the electrode surface of the lower electrode 4 is larger than that of the upper electrode 3. Furthermore, as illustrated in FIG. 3(c), ower electrode 4 can be disposed so that when the electrolysis device 15 is viewed in the direction B perpendicular to the electrode surface of the lower electrode 4, D>U≧S is satisfied, where D represents a protruding length on the downstream side, U represents a protruding length on the upstream side, and S represents a protruding length at the side. As illustrated in FIG. 3(b), when the electrolysis device 15 is viewed in the vertical direction A, the upper electrode 3 and the lower electrode 4 can be disposed so that the entire surface of the upper electrode 3 overlaps the lower electrode 4.

For example, in the case where an aqueous solution of a substance containing a chlorine atom is electrolyzed to produce hypochlorous acid using the lower electrode 4 as a cathode and the upper electrode 3 as an anode, if the electrode surface of the upper electrode 3 and the electrode surface of the lower electrode 4 have substantially the same area, the air bubbles of chlorine gas are dissolved and reduced around the upper electrode 3 because of a stirring and mixing effect produced by air bubbles and thus a decrease in the effective electrode area due to air bubbles is suppressed. However, such an effect is not produced at the lower electrode 4, and the effective electrode area is sometimes decreased by air bubbles of hydrogen gas. This relatively decreases the effective electrode area of the lower electrode 4, which is a rate-determining factor of the electrolysis reaction. Consequently, the area of the upper electrode 3 is sometimes not effectively utilized.

By increasing the electrode surface area of the lower electrode 4 more than the upper electrode 3, the above phenomenon can be relaxed. Consequently, the electrode surface area can be effectively utilized, and the electrolysis efficiency per unit area of the upper electrode 3 can be improved.

In the above configuration, when air bubbles of hydrogen gas generated on the upstream side of the lower electrode 4 come close to the upper electrode 3 serving as an anode and located above the lower electrode 4 in the vertical direction, the air bubbles can be brought into contact with an aqueous solution which has been electrolyzed on the upstream side of the upper electrode 3 and thus whose pH has been decreased. Therefore, chlorine gas can be efficiently converted into hypochlorous acid.

In the above configuration, even if hydrogen gas generated at the lower electrode 4 floats on the downstream side with respect to the vertically upward direction by the velocity of flow of a liquid, the hydrogen gas comes close to the upper electrode 3. This increases the fraction of chlorine gas converted into hypochlorous acid. In particular, even if an electric field on the downstream side of the upper electrode 3 is shielded by a large amount of air bubbles of hydrogen gas generated, the fraction of chlorine gas converted into hypochlorous acid can be expected to be increased to some degree by a fringing field to the electrode that extends to the downstream side or oxidation of air bubbles that have directly contacted the electrode.

Fourth Embodiment

FIG. 4 is a schematic sectional view of an electrolysis device according to the fourth embodiment.

The electrolysis devices 15 in FIGS. 1 to 3 include a linear channel 7 for fluid to be treated. However, in the electrolysis device 15 according to the fourth embodiment, the channel 7 for fluid to be treated includes an upstream-side bent channel 25 located close to the end of the interelectrode channel 6 on the upstream side or a downstream-side bent channel 26 located close to the end of the interelectrode channel 6 on the downstream side. The electrolysis device 15 may include both the upstream-side bent channel 25 and the downstream-side bent channel 26 or either the upstream-side bent channel 25 or the downstream-side bent channel 26.

For example, at least one of the flow inlet 8 and the flow outlet 9 can be disposed so that the direction of a channel near the flow inlet 8 or the flow outlet 9 is not parallel to the direction of the interelectrode channel 6. Thus, the upstream-side bent channel 25 or the downstream-side bent channel 26 can be disposed. In this configuration, a turbulent flow can be caused on a liquid in the channel 7 for fluid to be treated.

When the upstream-side bent channel 25 is disposed near the electrolysis electrode 5, the influence of a turbulent flow generated in the bent channel can be exerted on the interelectrode channel 6. This sufficiently produces a stirring effect from near the inlet where air bubbles are not so generated. Therefore, the diffusion of a substance near the electrode surface can be facilitated, and the electrolysis efficiency can be improved.

In the case where the downstream-side bent channel 26 is disposed, even if there is a gas not sufficiently dissolved at the interelectrode channel 6, stirring can be performed again at the bent channel. For example, when an aqueous solution of a substance containing a chlorine atom is electrolyzed to produce hypochlorous acid, chlorine gas is not sufficiently dissolved under some conditions, which sometimes decreases the production efficiency of hypochlorous acid. In this configuration, however, dissolution of chlorine gas and conversion into hypochlorous acid can be facilitated, and the electrolysis efficiency can be substantially improved.

The downstream-side bent channel 26 is preferably disposed so that air bubbles generated at the electrolysis electrode pair 5 are capable of floating to the flow outlet 9 by their buoyancy. Consequently, the air bubbles can be quickly discharged from the channel 7 for fluid to be treated. Thus, a decrease in the electrolysis efficiency due to holding of air bubbles can be suppressed.

Fifth Embodiment

FIG. 6(a) is a schematic sectional view of an electrolysis device according to the fifth embodiment. FIGS. 6(b) to 6(d) are schematic sectional views of constituent parts of the electrolysis device according to the fifth embodiment.

The electrolysis device 15 according to the fifth embodiment includes an assembly-type electrolysis unit 10. In the fifth embodiment, the electrolysis unit 10 is constituted by three parts. Two of the three parts are a first electrode holder 31 in FIG. 6(b) to which the lower electrode 4 is fixed and a second electrode holder 32 in FIG. 6(d) to which the upper electrode 3 is fixed. The remaining one is disposed as a spacer 33 between the first and second electrode holders 31 and 32. When viewed in a direction in which the electrolysis electrode pair 5 overlaps each other, at least part of the spacer 33 overlaps the electrolysis electrode pair 5. Furthermore, a protrusion 35 is disposed on each of the upstream side and the downstream side of the interelectrode channel 6. The upstream-side bent channel 25 and the downstream-side bent channel 26 are also disposed.

The spacer 33 is disposed so that the interelectrode channel 6 is formed between the upper electrode 3 and the lower electrode 4. The first electrode holder 31 at least has a recess to which the upper electrode 3 is to be fixed, and the second electrode holder 32 at least has a recess to which the lower electrode 4 is to be fixed. The distance (the depth of the recess) between the surface to which the upper electrode 3 or the lower electrode 4 is fixed and the surface in contact with the spacer 33 is preferably larger than the thickness of the electrode to be fixed. This produces a stirring effect on air bubbles and a liquid. Even if the electrode is warped or loosened for some reason, the probability that the upper electrode 3 and the lower electrode 4 are brought into contact with each other can be decreased. This improves the electrolysis efficiency and safety of the electrolysis device 15. Furthermore, the distance between the upper electrode 3 and the lower electrode 4 can be easily changed by changing the thickness of the spacer 33. Therefore, the specifications can be easily changed in accordance with the purposes of products, and thus commonality of parts such as an electrode holder is easily achieved. The metal holders 31 and 32 are made of a resin such as acrylic resin or vinyl chloride resin.

In the electrolysis device 15 in FIG. 6(a), a bolt 41 for fixing the upper electrode 3 and a bolt 41 for fixing the lower electrode 4 are electrode terminals 45. The bolt 41 is made of a metal material such as metal titanium.

FIGS. 7(a) and 7(b) are schematic sectional views for describing the flow of a fluid in the electrolysis device 15 in FIG. 6(a). FIG. 7(b) is a schematic sectional view of the electrolysis device 15 taken along dot-and-dash line F-F of FIG. 7(a).

It is generally found that, regarding the flow velocity in a channel, an average velocity V1 in a central portion is high and an average velocity V2 in a portion near the end is low. The amount of chemical change per unit volume by electrolysis, that is, the concentration k of a desired component produced by electrolysis is substantially proportional to the time t for which the electrolysis is performed as long as other conditions are the same. In other words, k∝t is given. When the electrode has a substantially rectangular shape and the central portion and the end portion have substantially the same length L in a direction of the average flow velocity, t=L/V and thus k∝L/V. Therefore, the concentration of a desired component generated in an aqueous solution flowing in the central portion is k1∝L/V1, and the concentration in the end portion is k2∝L/V2. When k1−k2 is used as an index of concentration variation, k1−k2=L(1/V1−1/V2) is given.

When the protrusion 35 is disposed upstream of the interelectrode channel 6 as illustrated in FIGS. 7(a) and 7(b), the protrusion 35 guides an obstacle and a fluid from the central portion to the end portion in the movement of liquid in the channel. Consequently, the amount of a fluid flowing per unit sectional area is small in the central portion and large in the end portion. Therefore, in a simplified system, the flow velocity in the central portion is V1−v on average and the flow velocity in the end portion is V2−v on average (v>0). The concentration variation herein is represented by k1−k2=L(1/(V1−v)−1/(V2−v)), and the concentration variation is small as long as V1−V2>v is satisfied.

Sixth Embodiment

FIG. 8 is a schematic sectional view of an electrolysis device according to the sixth embodiment. The electrolysis unit 10 included in the electrolysis device 15 in FIG. 8 includes at least the electrolysis electrode pair 5 and electrode holders 30 that define a channel other than the interelectrode channel 6. At least part of a member (an electrode terminal 45 in FIG. 8) including the protrusion 35 is connected to the electrolysis electrode pair 5, a base of the electrolysis electrode pair 5, or a member physically coupled with the electrolysis electrode pair 5. The at least part of the member is also connected to the electrode holders 30. By employing this connecting structure, the electrolysis electrode pair 5 can be fixed to the electrode holders 30. Therefore, the complication of the configuration and structure is prevented. The above connecting structure also reinforces the fixing of the electrolysis electrode pair 5 to the electrode holders 30. Thus, the reliability of the electrolysis unit 10 can be improved.

At least part of the protrusion 35 or the member coupled with the protrusion 35 (electrode terminal 45 in FIG. 8) is made of a conductive material, and at least part of the member may be electrically connected to the electrolysis electrode pair 5.

The member including the protrusion 35 may be disposed in the direction of the normal to a principal surface of the electrolysis electrode pair 5 that defines the channel 7 for fluid to be treated to connect the electrode holder and the electrode to each other.

For example, the protrusion 35 and the electrode terminal 45 may form a single member. The electrode holder 30 and the electrolysis electrode pair 5 have a hole with a size suitable for the electrode terminal 45 at a predetermined position. A groove is cut in at least a suitable portion of the electrode terminal 45 on the side opposite to the protrusion 35. The electrolysis electrode pair 5 can be fixed to the electrode holder 30 using a nut 42 suitable for the groove. At the same time, a voltage can be applied to the electrolysis electrode pair 5 from the outside of the electrode holder 30 through the electrode terminal 45. If necessary, an O-ring 47, a washer 48, and a spring washer 49 may be used to suppress liquid leakage.

Alternatively, for example, a female thread is cut in the hole of the electrode holder 30 and a male thread is cut on the electrode terminal 45, and the metal holder 30 and the electrode terminal 45 may be joined to each other by combining the female thread and the male thread. In this structure, the electrolysis electrode pair 5 can be fixed to the electrode holder 30 without using a nut.

Alternatively, for example, the electrode holder 30 and the electrode terminal 45 may be molded in one piece.

Since the electrolysis electrode pair 5 can be fixed to the electrode holder 30 and a voltage can be applied to the electrolysis electrode pair 5 by employing such a structure, a lead line for applying a voltage to the electrolysis electrode pair 5 is not additionally required. Therefore, the complication of the configuration and structure is prevented. Furthermore, the electrolysis electrode pair 5 can be fixed to the electrode holder 30 and a voltage can be applied to the electrolysis electrode pair 5 by a very simple method.

At least a portion of the surface of the protrusion 35 closest to the counter electrode may be nonconductive. For example, a nonconductive film can be formed by oxidizing the surface of the protrusion 35. Alternatively, the surface of the protrusion 35 may be coated with a resin or the like. This suppresses the progress of an electrochemical reaction on the surface of the protrusion 35, and also suppresses generation of undesired components and considerable variation in the concentration of a component generated.

Seventh Embodiment

FIG. 9(a) is a schematic sectional view of an electrolysis device according to the seventh embodiment. FIGS. 9(b) to 9(f) are schematic sectional views of constituent parts of the electrolysis device according to the seventh embodiment. FIG. 9(d) is a schematic sectional view of a spacer 33 taken along dot-and-dash line G-G of FIG. 9(c). FIG. 9(e) is a schematic sectional view of a spacer 33 taken along dot-and-dash line H-H of FIG. 9(c).

The electrolysis device 15 according to the seventh embodiment includes an assembly-type electrolysis unit 10. In the seventh embodiment, the electrolysis unit 10 is constituted by three parts. Two of the three parts are a first electrode holder 31 in FIG. 9(b) to which the lower electrode 4 is fixed and a second electrode holder 32 in FIG. 9(f) to which the upper electrode 3 is fixed. The remaining one is a spacer 33 in FIGS. 9(c) to 9(e) and is disposed between the first and second electrode holders 31 and 32. In the electrolysis device 15 in FIG. 9, an opening 36 of the spacer between the electrodes is formed with a size smaller than that of the electrolysis device 15 in FIG. 6. The spacer 33 is disposed so that the spacer 33 and the edges of the upper electrode 3 and lower electrode 4 overlap each other when view in a direction perpendicular to the electrode surface of the lower electrode 4. This suppresses the progress of an electrolysis reaction at an electrode edge where electric field concentration easily occurs and degradation also easily occurs. Thus, stable electrolysis can be performed, and electrode wear is suppressed, which increases the life of the electrolysis electrode pair 5.

Eighth Embodiment

FIGS. 10(a) and 10(b) are schematic views of electrolysis devices according to the eighth embodiment.

The electrolysis device 15 according to the eighth embodiment includes the electrolysis unit 10 according to one of the first to seventh embodiments, a raw solution tank 51, and a dilution unit 53. A pipe 57 is indicated by an arrow that also indicates a direction in which a fluid flows through the pipe. In the electrolysis device 15 in FIG. 10(a), a diluted solution is produced by injecting a solution subjected to electrolysis in the electrolysis unit 10 into stored water 55 in a dilution tank 54 serving as the dilution unit 53. In the electrolysis device 15 in FIG. 10(b), a diluted solution is produced by mixing a solution subjected to electrolysis in the electrolysis unit 10 with flowing water in a mixing unit 59 serving as the dilution unit 53. In FIGS. 10(a) and 10(b), wiring lines for supplying power to the electrolysis electrode pair 5 in the electrolysis unit 10, an optionally provided feeding pump, and the like are not illustrated.

In this configuration, a diluted solution containing an electrolysis product can be produced. When an aqueous solution of a substance containing a chlorine atom is electrolyzed to produce hypochlorous acid, a diluted solution can be produced while the release of chlorine gas is suppressed.

Ninth Embodiment

FIG. 11 is a schematic view of an electrolysis device according to the ninth embodiment. The electrolysis device 15 according to the ninth embodiment has the same configuration as the known electrolyzed water-producing device 120 illustrated in FIGS. 16 and 17, except that the electrolysis unit 10 disposed so that the electrolysis electrode pair 5 inclines with respect to the vertical direction is used. The fundamental operation of the electrolysis device 15 according to the ninth embodiment is also the same as that of the known electrolyzed water-producing device 120.

In the electrolysis device 15, desirably, a solenoid-controlled valve 66, the electrolysis unit 10, and a pump 68 are not operated upon turning a switch 64 ON, but the solenoid-controlled valve 66 is opened at an appropriate timing and water is supplied to the electrolysis device 15 from a feed water inlet 62, flows through a pipe 65, and is discharged from a discharge outlet 63. At an appropriate timing, the feeding pump 68 is operated and a raw electrolysis solution stored in a raw solution tank 67 is supplied to the electrolysis unit 10. Power is supplied to the electrolysis unit 10 from a power supply (not illustrated) at an appropriate timing, and the raw solution is electrolyzed. The high-concentration electrolyzed water produced by electrolysis is supplied to the pipe 65 and diluted to an appropriate concentration with water flowing through the pipe 65. The diluted electrolyzed water is fed to an electrolyzed water supply point through a pipe such as a hose suitably connected to the discharge outlet 63.

When the switch 64 is turned OFF, power supply to the solenoid-controlled valve 66, the feeding pump 68, and the electrolysis unit 10 is shut off at an appropriate timing, and the operation of the electrolysis device 15 is stopped.

In reality, an optimum sequence is set in accordance with the purpose. For example, with an interlock being provided, a solenoid-controlled valve is opened, a raw solution left in the electrolysis unit 10 during the previous operation is electrolyzed to a slight degree, and then a raw solution is started to be supplied.

For example, when the probability of initially producing high-concentration electrolyzed water needs to be decreased as much as possible, the solenoid-controlled valve 66, the feeding pump 68, and the electrolysis unit 10 are preferably turned ON in this order.

When the concentration of the electrolyzed water needs to be quickly increased, for example, the electrolysis unit 10, the feeding pump 68, and the solenoid-controlled valve 66 may be turned ON in this order.

In the case of stopping the operation, when rinsing with water needs to be performed after the electrolyzed water is used, the electrolysis unit 10 and the feeding pump 68 are turned OFF and then the ON-state of the solenoid-controlled valve 66 is kept for a predetermined time. Thus, rinsing can be performed for the predetermined time.

When the high-concentration electrolyzed water is prevented from remaining in the electrolysis unit 10, the electrolysis unit 10 is turned OFF and then the ON-state of the feeding pump 68 is kept for a while. Thus, the high-concentration electrolyzed water in the electrolysis unit 10 can be diluted with the raw electrolysis solution or almost all the high-concentration electrolyzed water can be replaced with the raw electrolysis solution. In this case, the solenoid-controlled valve 66 is also desirably turned ON. Obviously, additional amounts of raw solution and water are required in this case. Therefore, if such a repeated use is frequently performed, the electrolysis device is desirably designed so that such an operation is unnecessary.

Experimental Example 1

The electrolysis device illustrated in FIG. 1 was produced and an electrolysis experiment was performed with various inclination angles with respect to the vertical direction of the electrolysis electrode pair 5. The electrolysis electrode pair 5 included an electrode (referred to as a Ti electrode) formed of a titanium plate and having 8-cm long sides, 3-cm short sides, and a thickness of 1 mm and an electrode (referred to as an Ir-coated Ti electrode) obtained by coating a titanium plate having 8-cm long sides, 3-cm short sides, and a thickness of 1 mm with iridium oxide by a sintering method. The electrolysis electrode pair 5 was fixed to the casing 1 made of acrylic resin so that the Ti electrode and the Ir-coated Ti electrode were substantially parallel to each other and the interelectrode distance was in the range of 1 mm to 5 mm. Thus, an electrolysis device was produced. A power supply device and the electrolysis electrode pair 5 were connected to each other so that the Ti electrode served as a cathode and the Ir-coated Ti electrode served as an anode.

Each of electrolysis devices produced with various inclination angle of about −50° to +50° with respect to the vertical direction of the electrolysis electrode pair 5 was installed. A 3% to 4% aqueous sodium chloride solution was supplied at a constant flow rate to the channel 7 for fluid to be treated from the lower side. When the electrolysis electrode pair is disposed in a vertical direction, the inclination angle is 0°. When the electrolysis electrode pair is inclined so that the Ir-coated Ti electrode (anode) is brought on the upper side, the inclination angle is a positive angle. When the electrolysis electrode pair is inclined so that the Ir-coated Ti electrode is brought on the lower side, the inclination angle is a negative angle.

A constant current of 5 A was supplied to the electrolysis electrode pair 5 from the power supply device to electrolyze the aqueous sodium chloride solution. The voltage applied was between about 4 to 5 V. Furthermore, the effective chlorine concentration (mg/L) of the aqueous solution subjected to electrolysis was measured.

FIG. 12 shows the measurement result of the effective chlorine concentration. This result shows that when the electrolysis electrode pair 5 was inclined so that the Ir-coated Ti electrode serving as an anode was brought on the upper side, the effective chlorine concentration of the aqueous solution subjected to electrolysis could be increased. Specifically, when the electrolysis electrode pair 5 was inclined in the range of about 5° to 45°, the effective chlorine concentration was improved by about 5% compared with the case where the electrolysis electrode pair 5 was disposed in the vertical direction. When the electrolysis electrode pair 5 was inclined in the range of about 15° to 32°, the effective chlorine concentration was improved by about 10% compared with the case where the electrolysis electrode pair 5 was disposed in the vertical direction. If the electrolysis electrode pair 5 was excessively inclined, the effective chlorine concentration decreased. At an inclination angle of about 50°, the effective chlorine concentration was substantially equal to that in the case where the electrolysis electrode pair 5 was disposed in the vertical direction (0°).

Therefore, the electrolysis device is desirably disposed so that the electrolysis electrode pair 5 has an inclination angle of more than 0° and less than 50° with respect to the vertical direction. The inclination angle of the electrolysis electrode pair 5 is preferably 5° to 45° (improved by about 5%) and more preferably 15° to 32°. It was also found that when the electrolysis electrode pair 5 was disposed so that a part of the Ir-coated Ti electrode serving as an anode was located above the Ti electrode serving as a cathode in the vertical direction, the effective chlorine concentration of the aqueous solution subjected to electrolysis could be increased, and thus the electrolysis efficiency could be improved.

The same experiment was conducted by using various electrode materials for generating chlorine, using an aqueous solution containing a chloride, such as an aqueous sodium chloride solution, hydrochloric acid, or a mixture of the aqueous sodium chloride solution and hydrochloric acid, changing the amount of the aqueous solution fed, and changing the electrolysis conditions (voltage and current). The same tendency was observed in all the experiments. In some cases, the effective chlorine concentration in the vertical direction (0°) and the effective chlorine concentration at an optimum angle (0° to about 50°) were substantially equal to each other in the range of measurement errors. Even in this case, however, the effective chlorine concentration was clearly decreased when the electrolysis electrode pair was inclined so that the cathode was brought on the upper side. The effective chlorine concentration tended to decrease by about 10% at about 23° and by about 20% at about 45° as in FIG. 12. Therefore, 0° may be an optimum angle under some electrolysis conditions, but the electrolysis electrode pair is preferably inclined to some degree so that the anode is brought on the upper side. This is because, in addition to the assembly tolerance established when an electrolysis device is installed to an apparatus, the apparatus is not necessarily used at a strictly horizontal place in reality. Therefore, when the electrolysis electrode pair is inclined to the anode side or the cathode side with respect to the vertical direction (0°) by the same degree, the electrolysis device is preferably installed while the electrolysis electrode pair is inclined in advance so that a decrease in the effective chlorine concentration is suppressed or the effective chlorine concentration increases. The optimum inclination varies in accordance with the structure of the electrolysis device, the composition of an aqueous solution to be electrolyzed, the amount of a solution fed, the electrolysis conditions, and the like. Furthermore, as described above, for example, vibration, swinging, and inclination occur in a practical environment. In view of the foregoing, for example, when a margin of 5° is given in an intended usage situation, the electrolysis device is preferably installed at an optimum angle in the range of 5° to 45°. Typically, the optimum angle is expected to be in the range of 20° to 30°. However, the electrolysis electrode pair can be used at an inclination angle of up to 45° to decrease the height of an apparatus to which the electrolysis device is installed.

In Experimental Example 1, an acrylic resin having high transparency was used for the casing 1 to observe the state of bubbles. However, it is obvious that the casing 1 may be made of any material as long as the material has resistance to, for example, the aqueous solution supplied to the electrolysis device, various substances generated by electrolysis, and generated gas. If desired reliability is achieved, polypropylene or the like can be used. In the case where a chlorine-based aqueous solution or gas is generated as in Experimental Example 1, the material for the casing 1 is most preferably a vinyl chloride resin in terms of high resistance, workability, and low cost.

Although the reason for which the electrolysis efficiency is improved by inclining the electrolysis electrode pair 5 so that a part of the anode is located above the cathode in the vertical direction is still unclear, the following hypothesis is proposed.

In the cathode, it is believed that an electrode reaction represented by the above reaction formula (4) proceeds and H₂ is generated. The generated H₂ is relatively not easily dissolved and almost all the generated H₂ is present in the form of air bubbles. Since the cathode is located below the anode in the vertical direction because of the inclination of the electrolysis electrode pair 5, the air bubbles of H₂ are believed to leave from the cathode because of their buoyancy and move to near the anode. Therefore, the air bubbles generated at the cathode move so as to cross the aqueous solution flowing in the flow velocity direction, and thus stirring of the aqueous solution near the cathode and the aqueous solution near the anode is facilitated. The air bubbles of H₂ move to near the anode and also an alkalescent aqueous solution near the cathode is moved to near the anode. Therefore, the conversion of chlorine gas into hypochlorous acid or the like represented by the above reaction formula (2) is facilitated. Furthermore, the movement of the aqueous solution near the cathode on the upstream side toward the anode is facilitated with the movement of the air bubbles. Consequently, the fraction of a liquid component subjected to electrolysis is decreased in the aqueous solution near the cathode on the downstream side, which effectively works for electrolysis.

FIG. 13 is a schematic view of an interelectrode channel in the case where the electrolysis electrode pair has an inclination angle of 0°. When the electrolysis electrode pair is disposed at an inclination angle of 0°, the direction in which the aqueous solution flows through the interelectrode channel from the lower side to the upper side matches the direction in which air bubbles generated on the electrode surface by an electrolysis reaction float from the lower side to the upper side. Therefore, as indicated by arrows in FIG. 13, the aqueous solution and the air bubbles close to the cathode flow through the interelectrode channel while they are not easily mixed with each other. The aqueous solution and the air bubbles close to the anode also flow through the interelectrode channel while they are not easily mixed with each other.

In the case where the electrolysis electrode pair is inclined with respect to the vertical direction so that the anode serves as an upper electrode, if electrolysis is not performed and air bubbles are not generated, an aqueous solution is believed to flow as in FIG. 13. However, when electrolysis is performed, in particular, when air bubbles are generated, the situation is totally different.

In the case where air bubbles float from the cathode toward the anode in the aqueous solution, the air bubbles and the aqueous solution having different velocity vectors are resistant to each other and their momentums are exchanged. For example, it is well-known that air bubbles in still water move upward because of their buoyancy and a stream of water is generated along with the movement.

A force of upward movement due to buoyancy is exerted on the air bubbles generated in the inclined interelectrode channel, that is, in the aqueous solution having a diagonal flux. Therefore, the direction in which the air bubbles move is not parallel with the direction in which the aqueous solution flows. The air bubbles move in a direction from the lower electrode (cathode) toward the upper electrode (anode), and the direction in which the air bubbles move is more upward than the direction in which the aqueous solution flows. Herein, the aqueous solution also moves in a direction from the lower electrode (cathode) toward the upper electrode (anode) along with the movement of the air bubbles. This generates a flow that causes the aqueous solution near the cathode to move to near the anode. Consequently, products on the anode side and products on the cathode side are mixed well.

Next, the case where the electrolysis electrode pair is inclined so that the cathode serves as an upper electrode, that is, the case of a negative inclination angle on a graph in FIG. 12 will be discussed. Air bubbles generated at the anode serving as a lower electrode are chlorine gas and oxygen gas as represented by the above reaction formulae (1) and (3), and the chlorine gas readily dissolves in water and hypochlorous acid is produced as represented by the above reaction formula (2). Therefore, the amount of air bubbles generated at the cathode serving as a lower electrode is smaller than that of air bubbles of H₂ gas generated at the cathode serving as an upper electrode. Thus, the air bubbles generated at the lower electrode do not produce a large stirring effect. A relatively large amount of air bubbles generated at the cathode serving as an upper electrode move along the surface of the cathode. This increases the surface area of the cathode coated with the air bubbles, inhibits the contact between the cathode and the aqueous solution, and decreases the electrolysis efficiency. This is believed to be disadvantageous for electrolysis.

In Experimental Example 1, a preferred result was obtained by setting the anode as an upper electrode. However, it is found from this hypothesis that the electrolysis efficiency can be improved depending on a substance to be electrolyzed by setting, as a lower electrode, an electrode at which a relatively large amount of air bubbles is generated and setting, as an upper electrode, an electrode at which a relatively small amount of air bubbles is generated.

To confirm the hypothesis, there were produced an electrolysis device in which the inclination angle of the electrolysis electrode pair was set to 0° and the upper end of the Ir-coated Ti electrode serving as an anode 21 was 1 cm higher than the upper end of the Ti electrode serving as a cathode 22 as illustrated in FIG. 14(b) and an electrolysis device in which the inclination angle of the electrolysis electrode pair was set to 0° and the upper end of the cathode 22 was 1 cm higher than the upper end of the anode 21 as illustrated in FIG. 14(c). An electrolysis experiment was conducted by supplying an aqueous sodium chloride solution to the channel 7 for fluid to be treated in each of the electrolysis devices from the lower side at a constant flow rate and supplying a constant current of 5 A between the cathode 22 and the anode 21. Other experimental conditions and measurement methods were the same as those of the above electrolysis experiment.

In the electrolysis experiment that used the electrolysis device in which the anode 21 was brought on the upper side, the effective chlorine concentration (mg/L) of the aqueous solution subjected to electrolysis was about 65 mg/L. In the electrolysis experiment that used the electrolysis device in which the cathode 22 was brought on the upper side, the effective chlorine concentration (mg/L) of the aqueous solution subjected to electrolysis was about 60 mg/L. As a result, an electrolysis reaction product was obtained in the experiment that used the electrolysis device in which the anode 21 was brought on the upper side with an efficiency about 10% higher than the efficiency in the experiment that used the electrolysis device in which the cathode 22 was brought on the upper side.

When air bubbles are not generated as illustrated in FIG. 14(a), a stirring and mixing effect produced by air bubbles cannot be expected. When the amounts of air bubbles generated on both sides are substantially the same, an effect produced by air bubbles is believed to be substantially the same regardless of which electrode is brought above.

However, the situation is different when the anode 21 and the cathode 22 having different amounts of air bubbles generated as in this experiment are used. In this experiment, since chlorine gas mainly generated at the anode 21 dissolves in the aqueous solution well and the amount of air bubbles is small, the amount of air bubbles generated at the cathode 22 at which hydrogen gas is generated is larger than that at the anode 21. This state is schematically illustrated in FIG. 14(b) and FIG. 14(c). In the case where the anode 21 is brought on the upper side as illustrated in FIG. 14(b), if the amount of air bubbles generated at the cathode 22 is sufficiently large, it is expected that the air bubbles move to near the anode, which produces a stirring and mixing effect on the aqueous solution.

When the cathode 22 is brought on the upper side as illustrated in FIG. 14(c), air bubbles generated at the cathode 22 cannot move to near the anode, a stirring and mixing effect of the air bubbles on the aqueous solution is expected to be smaller than that at least in the case of FIG. 14(b). When the stirring and mixing effect is small, the aqueous solution subjected to electrolysis on the lower side of the anode moves upward along the electrode surface of the anode, and therefore the electrolysis efficiency is expected to decrease on the upper side of the anode. When the stirring and mixing effect is large, a fresh raw solution is supplied to the surface of the anode, and therefore the electrolysis efficiency is expected to increase. Accordingly, the stirring and mixing effect of air bubbles on the aqueous solution qualitatively matches the experimental results.

In this experiment, a preferred result was obtained by bringing the anode 21 on the upper side. However, it is found from this hypothesis that the electrolysis efficiency can be improved depending on a substance to be electrolyzed by bringing, on the lower side, an electrode at which a relatively large amount of air bubbles is generated and bringing, on the upper side, an electrode at which a relatively small amount of air bubbles is generated.

Experimental Example 2

A “vertically discharged” electrolysis unit 10 including the flow inlet 8 and the flow outlet 9 in a channel direction of the interelectrode channel 6 as illustrated in FIG. 1 was produced. A “horizontally discharged (upward)” electrolysis unit 10 including the upstream-side bent channel 25 and the downstream-side bent channel 26 so that the flow outlet 9 faces upward as illustrated in FIG. 4 was produced. A “horizontally discharged (downward)” electrolysis unit 10 including the upstream-side bent channel 25 and the downstream-side bent channel 26 so that the flow outlet 9 faces downward as illustrated in FIG. 5 was produced. An electrolysis experiment was conducted.

In the electrolysis experiment, electrolysis was performed using the electrolysis electrode pair 5 by installing the electrolysis device 15 so that the electrolysis electrode pair 5 had inclination angles of about 23° and about 45° with respect to the vertical direction and supplying a 3% to 4% aqueous sodium chloride solution to the channel 7 for fluid to be treated from the lower side at a constant flow rate. The effective chlorine concentration (ppm) of the aqueous solution subjected to electrolysis was measured. Other conditions were the same as those in Experimental Example 1. Table 1 shows the results of the electrolysis experiment.

As is clear from Table 1, the electrolysis efficiency of the “horizontally discharged (upward)” electrolysis device is high. The reason for this is unclear, but may be as follows. When the upstream-side channel close to the end of the interelectrode channel on the upstream side is bent to some degree or the downstream-side channel close to the end of the interelectrode channel on the downstream side is bent to some degree, the flux or the flow of air bubbles is randomized and thus the electrolysis efficiency may be improved.

To smoothen the flow of air bubbles after a fluid is bent, the channels on the inlet and outlet sides, in particular, the channel on the outlet side may be caused to extend in the vertical direction as illustrated in FIG. 20(a).

From the viewpoint of ease of mass production, as a modification, the vertical direction may be made by using a pipe unit 70 as illustrated in FIGS. 20(b) and 20(c).

TABLE 1 Horizontally Horizontally Vertically discharged discharged Inclination discharged (upward) (downward) angle electrolysis unit electrolysis unit electrolysis unit 23° 73 ppm 77 ppm 70 ppm 45° 66 ppm 73 ppm 59 ppm

Experimental Example 3

An electrolysis unit 10 illustrated in FIG. 6(a) was produced and an electrolysis experiment was conducted. The produced electrolysis unit 10 is constituted by three parts illustrated in FIGS. 6(b) to 6(d). Two of the three parts are electrode holders 31 and 32 having the same shape and disposed symmetrically about a point. The remaining one is a spacer 33 disposed between the two electrode holders. When viewed in a direction in which the electrolysis electrode pair 5 overlaps each other, at least part of the spacer 33 overlaps the electrolysis electrode pair 5.

In the produced electrolysis unit 10, a titanium bolt 41 including a protrusion 35 was used. The electrode holders 31 and 32 and the spacer 33 were made of acrylic resin. The upper electrode 3 serving as an anode was an insoluble electrode (manufactured by DAISO ENGINEERING Co., Ltd.) for producing sodium hypochlorite. The lower electrode 4 serving as a cathode was a titanium plate manufactured by The Nilaco Corporation. The three parts were assembled so that the interelectrode distance was in the range of 1 mm to 5 mm by adjusting the thickness of the spacer 33. In Experimental Example 2, since the electrode holders and the like are made of acrylic resin, the inside of the electrolysis unit 10 can be observed. Herein, the acrylic resin does not transmit light with a short wavelength, in particular, UV light. This is to reduce the influence caused by light as much as possible. Therefore, a material that does not transmit light at all is preferably used in actual products.

The electrode holders 31 and 32 and the spacer 33 were fixed using a bolt 41 and a nut 42 together with a washer, a spring washer, and an O-ring (not illustrated). In Experimental Example 2, the electrolysis unit 10 can be disassembled. From the viewpoint of long-term reliability, a strong adhesive or the like is preferably used for the adherend of the electrolysis unit 10 to prevent the leakage of an electrolysis solution. By using an airtight gasket with chemical resistance as the spacer 33, both thickness adjustment and sealing can be performed. To reduce the cost by mass production, the electrolysis unit 10 can also be produced at a time by molding the parts in one piece.

For comparison, an electrolysis unit that did not include a protrusion 35 was also produced and an electrolysis experiment was conducted. Other configuration was the same as that of the electrolysis unit 10.

Electrolysis was performed while a 3% to 4% aqueous NaCl solution was supplied to the channel 7 for fluid to be treated of the produced electrolysis unit 10 at 5 to 80 ml/min. The electrolysis could be performed with a higher electrolysis efficiency in the electrolysis unit 10 including the protrusion 35 than in the electrolysis unit that did not include the protrusion 35.

Experimental Example 4

An electrolysis unit 10 illustrated in FIG. 9(a) was produced and an electrolysis experiment was conducted. The produced electrolysis unit 10 is constituted by parts illustrated in FIGS. 9(b) to 9(f). The size of an opening in the spacer 33 is smaller than that of the electrolysis unit 10 illustrated in FIG. 6. The spacer 33 is disposed so that the spacer 33 and the edges of the upper electrode 3 and lower electrode 4 overlap each other.

When a solution to be electrolyzed was an aqueous sodium chloride solution, the electrolysis efficiency was substantially the same as that in Experimental Example 3. However, when the electrolysis solution was obtained by adding hydrochloric acid to an aqueous sodium chloride solution to make the solution acidic, the concentration of hypochlorous acid produced in the electrolysis unit 10 in FIG. 9 was high and the variation in concentration was small. Therefore, the electrolysis efficiency and the stability of the concentration of a substance produced were considerably improved by employing the configuration in FIG. 9.

This may be because, by employing the configuration in FIG. 9, an electrolysis reaction relatively evenly proceeds at the electrolysis electrode pair 5 and stirring is also relatively uniformly performed. Furthermore, when the channel 7 for fluid to be treated has the configuration illustrated in FIG. 9, stirring and homogeneity of a fluid to be treated are achieved at a place other than the interelectrode channel 6. Thus, the substantial efficiency and stability are believed to be improved.

Experimental Example 5

A diluted solution containing an electrolysis product was produced using electrolysis devices 15 illustrated in FIGS. 10(a) and 10(b). The raw electrolysis solution 52 was a 3% to 4% aqueous NaCl solution, and electrolysis was performed using the electrolysis unit 10 illustrated in FIG. 6(a) under conditions that 4000 ppm of hypochlorous acid was theoretically produced. The treated aqueous solution was diluted with pure water in the dilution unit 53 to produce a diluted solution. For comparison, a known electrolysis unit including an electrolysis electrode pair having an electrode surface parallel to the vertical direction was installed to the electrolysis device in FIG. 10(a) to produce a diluted solution.

In the electrolysis experiment using the known electrolysis unit, chlorine gas did not sufficiently dissolve in the aqueous solution in an acidic region of pH 7 or less. Even when air bubbles were caused to pass through pure water for dilution in the dilution tank, the chlorine gas concentration near the surface of the diluted solution was more than 0.5 ppm and in some cases 2 ppm or more. The production of hypochlorous acid with high concentration and low pH by electrolysis was not put to practical use. This may be because, in a known method, chlorine gas was generated at low pH, which made difficult to efficiently produce a high-concentration liquid by electrolysis.

In the electrolysis experiment using the electrolysis device 15 in FIG. 10(a) according to Experimental Example 5, the produced diluted solution had a pH of 6 to 8, a hypochlorous acid concentration of 1000 ppm or more, and a chlorine gas concentration of 0.5 ppm or less near the surface of the diluted solution. In the electrolysis device 15 of Experimental Example 5, therefore, the release of chlorine gas was considerably suppressed compared with comparative examples. In the electrolysis device 15 of Experimental Example 5, chlorine gas generated by electrolysis efficiently dissolves in the aqueous solution, and thus the time required until the concentration of hypochlorous acid in the diluted solution exceeds 1000 ppm was considerably shortened.

In the electrolysis experiment using the electrolysis device 15 in FIG. 10(b) according to Experimental Example 5, the chlorine gas concentration measured near the end of the pipe 57 through which the diluted solution was discharged was 0.5 ppm or less.

Experimental Example 6

An electrolysis device illustrated in FIG. 19 was produced. An electrolysis experiment was performed with various inclination angles with respect to the vertical direction of the electrolysis electrode pair 5 as in Experimental Example 1. The electrolysis electrode pair 5 included an electrode (referred to as a Ti electrode) formed of a titanium plate and having 5-cm long sides, 1-cm short sides, and a thickness of 1 mm and an electrode (referred to as an Ir-coated Ti electrode) obtained by coating a titanium plate having 5-cm long sides, 1-cm short sides, and a thickness of 1 mm with iridium oxide by a sintering method. The electrolysis electrode pair 5 was fixed to the casing 1 made of acrylic resin so that the Ti electrode and the Ir-coated Ti electrode were substantially parallel to each other and the interelectrode distance was in the range of 1 mm to 5 mm. Thus, an electrolysis device was produced. A power supply device 72 and the electrolysis electrode pair 5 were connected to each other so that the Ti electrode served as a cathode and the Ir-coated Ti electrode served as an anode.

In Experimental Example 6, the electrolysis electrode pair 5 was installed to a so-called batch-type electrolytic cell 74 with various inclination angles of about −60° to about +60° with respect to the vertical direction, unlike a closed channel electrolysis unit in Experimental Example 1 in which electrodes define a part of a channel and a fluid to be treated is supplied in substantially the same direction. A 3% to 4% aqueous sodium chloride solution was charged into the electrolytic cell 74. When the electrolysis electrode pair 5 is disposed in a vertical direction, the inclination angle is 0°. When the electrolysis electrode pair 5 is inclined so that the Ir-coated Ti electrode (anode) is brought on the upper side, the inclination angle is a positive angle. When the electrolysis electrode pair 5 is inclined so that the Ir-coated Ti electrode is brought on the lower side, the inclination angle is a negative angle.

A constant current of 1 A was supplied to the electrolysis electrode pair 5 from the power supply device 72 to electrolyze the aqueous sodium chloride solution. The voltage applied was between about 4 to 5 V. Furthermore, the effective chlorine concentration (mg/L) of the aqueous solution subjected to electrolysis was measured.

FIG. 18 illustrates the measurement result of the effective chlorine concentration. This result shows that the effective chlorine concentration of the aqueous solution subjected to electrolysis could be improved by inclining the electrolysis electrode pair 5 so that the Ir-coated Ti electrode serving as an anode was brought on the lower side as opposed to Experimental Example 1. Specifically, when the electrolysis electrode pair 5 was inclined at least up to about −60°, the effective chlorine concentration was improved compared with the case where the electrolysis electrode pair 5 was disposed in the vertical direction. When the electrolysis electrode pair 5 was inclined in the range of about −20° to about −45°, the effective chlorine concentration was improved by about 5% compared with the case where the electrolysis electrode pair 5 was disposed in the vertical direction. If the electrolysis electrode pair 5 was excessively inclined, the effective chlorine concentration tended to decrease. The effective chlorine concentration at about −60° was substantially the same as that in the vertical direction (0°).

Therefore, the electrolysis electrode pair 5 is desirably installed to the electrolytic cell 74 so as to have an inclination angle of more than 0° and less than 60° and preferably 20° to 45° (about 5% improvement) with respect to the vertical direction. It was also found that the effective chlorine concentration of the aqueous solution subjected to electrolysis could be improved by disposing the electrolysis electrode pair 5 so that a part of the Ir-coated Ti electrode serving as an anode was located below the Ti electrode serving as a cathode in the vertical direction, and thus the electrolysis efficiency could be improved.

The direction of the electrolysis electrode pair 5 is either a direction in which the short sides extend horizontally or a direction in which the long sides extend horizontally. In both the directions, the electrolysis efficiency was improved when the electrolysis electrode pair 5 was inclined so that the cathode was brought on the upper side.

In such a batch-type electrolytic cell 74, the electrolysis efficiency is improved by inclining the electrolysis electrode pair 5 so that a part of the anode located below the cathode in the vertical direction, unlike the closed channel electrolysis unit. The reason for the difference is unclear, but the following hypothesis is considered.

It is believed that at the cathode, an electrode reaction proceeds and H₂ is generated as in Experimental Example 1. The generated H₂ relatively does not easily dissolve and thus almost all the H₂ is present in the form of air bubbles.

The batch-type electrolytic cell 74 having a large open area including the area of side surfaces produces only a small confinement effect compared with the closed electrolysis unit. Therefore, the average time for which air bubbles of H₂ are present between the electrodes is short, and a fresh substance to be electrolyzed is spontaneously supplied to replace air bubbles of H₂. Consequently, the electrolysis efficiency is believed to be improved.

The amount of the spontaneously supplied substance to be electrolyzed is not particularly limited, the concentration after electrolysis between the electrodes, that is, the concentration of hypochlorous acid is kept relatively low. The chlorine gas generated at the anode and left without being converted into hypochlorous acid rises because of its buoyancy and moves toward the cathode. Herein, an alkalescent aqueous solution near the cathode moves more slowly than air bubbles of H₂ and chlorine gas. Therefore, a chance of contact between the alkalescent aqueous solution and chlorine gas that has come from the anode increases, which facilitates the conversation of the chlorine gas into hypochlorous acid and the like.

When the cathode is brought on the lower side, air bubbles of H₂ generated move toward the anode because of their buoyancy and a space between the electrodes is filled with the air bubbles of H₂. In some cases, the air bubbles adhere to and remain on the anode, which considerably decreases the area of the anode that contacts the substance to be electrolyzed. In the experiment, at an angle of 80° or more, almost all the surface of the anode was covered with air bubbles of H₂ and the electrolysis efficiency was considerably decreased. The electrolysis efficiency is believed to be decreased by, for example, a decrease in the amount of the substance to be electrolyzed between the electrodes, a decrease in the effective electrode surface area due to air bubbles, and the inhibition of flow-in of a fresh substance to be electrolyzed.

The aqueous solution near the anode and the chlorine gas generated at the anode flow out so as to be forced out by the air bubbles of H₂ from the space between the electrodes to an open surface such as a side surface. Therefore, the stirring of the aqueous solution near the cathode and the aqueous solution near the anode is not facilitated unlike the closed electrolysis unit, and the conversation of chlorine gas into hypochlorous acid and the like is also not facilitated. In some cases, the chlorine gas itself is released from the substance to be electrolyzed to a space, and thus the effective chlorine concentration is believed to be decreased.

In the case of the closed electrolysis unit, the air bubbles of H₂ is held between the electrodes regardless of the manner of inclination and the supply amount of a substance to be electrolyzed is limited. In such a closed electrolysis unit, when the cathode is brought on the upper side, the separation of H₂ from the cathode is delayed. Consequently, the effective electrode area of the cathode is decreased by an H₂ covering effect and the approach of the substance to be electrolyzed near the surface of the cathode is prevented. Thus, the electrolysis efficiency is believed to be decreased. When the cathode is brought on the lower side, the separation of H₂ is facilitated. Consequently, the decrease in the effective electrode area of the cathode due to an H₂ covering effect is suppressed and a fresh substance to be electrolyzed is supplied to the surface of the cathode. Furthermore, the air bubbles of H₂ move to near the anode and the alkalescent aqueous solution near the cathode is also carried to near the anode. Thus, the conversation of chlorine gas into hypochlorous acid and the like is facilitated. Furthermore, the movement of the aqueous solution located upstream of the cathode in the direction toward the anode is facilitated with the movement of the air bubbles. Therefore, the aqueous solution located downstream of the cathode contains a small fraction of a liquid component subjected to electrolysis. This effectively works for electrolysis.

In the closed electrolysis unit, the amount of the substance to be electrolyzed that is supplied to the electrolysis unit is limited. Therefore, the concentration of the electrolyzed substance, that is, the concentration of hypochlorous acid in this Experimental Example tends to increase. An excessive increase in the concentration of hypochlorous acid decreases the electrolysis efficiency. To prevent this, at least part of chlorine gas generated at the anode is released from the outlet without being converted into hypochlorous acid in the electrolysis unit and converted into hypochlorous acid through contact with water after the dilution unit. Consequently, the increase in the concentration of hypochlorous acid in the electrolysis unit is suppressed. Thus, the electrolysis efficiency is believed to be improved.

As described above, the conditions that the electrolysis efficiency is improved vary depending on the cases.

The case where the electrode pair is desirably inclined so that the anode is located above the cathode is as follows: (i) a closed electrolysis unit is employed in which the electrodes substantially serve as an electrolytic cell or constitute a part of wall surfaces of a channel, (ii) the electrolysis unit includes an inlet for substances to be electrolyzed and an outlet for substances produced by electrolysis and unelectrolyzed substances, and (iii) the electrolysis unit includes at least one of means for supplying the substances to be electrolyzed from the inlet by force and means for drawing out the substances produced by electrolysis and the unelectrolyzed substances from the outlet by force.

Examples of the means for supplying the substance by force include feeding the substance to the inlet with a pump, suctioning the substance from the outlet with a pump, employing a structure in which a Venturi effect is produced by the dilution unit and the periphery thereof and suctioning the substance from the outlet, and disposing a tank on the upper side and feeding the substance by gravity. A pump is preferably used because the most stable feeding can be achieved. If variation is allowable to some degree, a structure that uses a Venturi effect or gravity is preferably employed without using a pump because energy for operating a pump is unnecessary, which saves the energy and reduces the cost of the pump. Obviously, some or all of the pump, the Venturi effect, and the gravity may be combined with each other.

For example, Experimental Example 1 employs a structure in which a tube pump is used to supply a substance at a constant rate as much as possible.

When at least one of (a) the case where electrolysis is performed in which air bubbles are generated at the cathode, (b) the case where a substance generated at the anode or a substance obtained by a chemical reaction of the substance is obtained, (c) the case where the outlet of the electrolysis unit includes a dilution unit, and (d) the case where the concentration of a substance produced by electrolysis is relatively high in the electrolysis unit is satisfied, the electrode pair is believed to be desirably inclined so that the anode is located above the cathode. When a plurality of (a) to (d) are satisfied or when all of (a) to (d) are satisfied, the electrode pair is also believed to be desirably inclined so that the anode is located above the cathode.

If there is no means for supplying the substance to be electrolyzed to a space between the electrodes by force or no means for suctioning the substance by force in a structure in which the electrolysis electrode pair is substantially disposed in the stored substance to be electrolyzed, the electrode pair is believed to be desirably inclined so that the anode is located below the cathode.

In this structure, the substance to be electrolyzed is supplied in a passive manner with the rise of air bubbles.

Chlorine gas unconverted into hypochlorous acid is easily released to a gas phase within a short time compared with the case where the closed electrolysis unit is employed.

The release to a gas phase is further suppressed in the closed electrolysis unit because there are many factors of facilitating conversation into hypochlorous acid. For example, the supply amount of the substance to be electrolyzed is limited and thus conversation into hypochlorous acid is easily caused by a confinement effect in the electrolysis unit and a stirring effect produced by air bubbles of H₂. Furthermore, conversation of chlorine gas into hypochlorous acid in the dilution unit is facilitated. In addition, conversation of chlorine gas into hypochlorous acid is also caused in a line through which dilution water flows after the dilution unit.

REFERENCE SIGNS LIST

-   -   1 casing     -   3 upper electrode     -   4 lower electrode     -   5 electrolysis electrode pair     -   6 interelectrode channel     -   7 channel for fluid to be treated     -   8 flow inlet     -   9 flow outlet     -   10 electrolysis unit     -   11 air bubbles     -   15 electrolysis device     -   16 overlap region when viewed in vertical direction     -   17 overlap region when viewed in direction perpendicular to         principal surface of lower electrode     -   21 anode     -   22 cathode     -   25 upstream-side bent channel     -   26 downstream-side bent channel     -   30 electrode holder     -   31 first electrode holder     -   32 second electrode holder     -   33 spacer     -   35 protrusion     -   36 opening of spacer     -   37 groove of electrode holder     -   41 bolt     -   42 nut     -   43 clearance hole     -   45 electrode terminal     -   47 O-ring     -   48 washer     -   49 spring washer     -   51 raw electrolysis solution tank     -   52 raw electrolysis solution     -   53 dilution unit     -   54 dilution tank     -   55 stored water     -   57 pipe     -   59 mixing unit     -   61 casing     -   62 feed water inlet     -   63 discharge outlet     -   64 switch     -   65 pipe     -   66 solenoid-controlled valve     -   67 raw solution tank     -   68 pump     -   70 pipe unit     -   72 power supply device     -   74 electrolytic cell     -   75 fluid to be treated     -   77 wiring line     -   100 electrolysis device     -   101 casing     -   103 first electrode     -   104 second electrode     -   106 first wiring line     -   107 second wiring line     -   108 supply inlet     -   109 discharge outlet     -   111 casing     -   112 feed water inlet     -   113 discharge outlet     -   114 switch     -   115 pipe     -   116 solenoid-controlled valve     -   117 raw solution tank     -   118 pump     -   120 electrolyzed water-producing device 

1. An electrolysis device comprising: an electrolysis unit, wherein the electrolysis unit includes a channel for fluid to be treated, at least one electrolysis electrode pair, a flow inlet, and a flow outlet, the electrolysis electrode pair is disposed so as to incline with respect to a vertical direction and includes an upper electrode and a lower electrode disposed so as to face each other, and the channel for fluid to be treated is disposed so that a fluid that has flowed in from the flow inlet flows through an interelectrode channel between the upper electrode and the lower electrode from a lower side to an upper side and flows out from the flow outlet.
 2. The electrolysis device according to claim 1, wherein the electrolysis electrode pair is disposed so as to have an inclination angle of more than 0° and less than 50° with respect to the vertical direction.
 3. The electrolysis device according to claim 1 or 2, wherein the channel for fluid to be treated includes an upstream-side bent channel located close to an end of the interelectrode channel on an upstream side or a downstream-side bent channel located close to an end of the interelectrode channel on a downstream side.
 4. The electrolysis device according to any one of claims 1 to 3, further comprising means for supplying, by force, a fluid to the channel for fluid to be treated, wherein the electrolysis electrode pair is disposed so that an electrode reaction that generates gases proceeds at the lower electrode and the upper electrode, and an amount of a gas generated at the lower electrode and released outside is substantially larger than that of a gas generated at the upper electrode and released outside.
 5. The electrolysis device according to any one of claims 1 to 4, wherein the upper electrode serves as an anode, and the lower electrode serves as a cathode.
 6. The electrolysis device according to any one of claims 1 to 5, wherein the lower electrode has an electrode surface area larger than that of the upper electrode.
 7. The electrolysis device according to any one of claims 1 to 6, further comprising a dilution unit, wherein the fluid is an aqueous solution, the electrolysis electrode pair is disposed so that a hypochlorite ion is electrochemically produced from a chlorine-containing compound contained in the aqueous solution, the aqueous solution at the flow outlet contains 4000 ppm or more of a hypochlorite ion on a weight basis, the dilution unit is disposed so as to produce a diluted solution of the aqueous solution that contains a hypochlorite ion and is discharged from the flow outlet, and the diluted solution has a pH of 7.5 or less.
 8. The electrolysis device according to any one of claims 1 to 3, wherein the channel for fluid to be treated is disposed so that a fluid is supplied to the channel for fluid to be treated by convection, the electrolysis electrode pair is disposed so that an electrode reaction that generates gases proceeds at the lower electrode and the upper electrode, and an amount of a gas generated at the upper electrode and released outside is substantially larger than that of a gas generated at the lower electrode and released outside. 